(CNN) -- A preliminary session of Syrian peace talks meant to end three years of bloodshed was an important "first, small step," U.N. Secretary-General Ban Ki-moon said Wednesday after a morning of bitter exchanges.
Speaking to reporters after the first leg of talks, Ban said a "difficult road" lay ahead, but the time had come for negotiations.
"We did not expect instant breakthroughs from today's conference, but the seriousness and horror of the situation has focused all minds, and there is a determination that all parties will find a way to peace," he said.
"We have a difficult road ahead, but it can be done and it must be done. It is still not too late to end the bloodshed and find the peaceful and democratic future. The moment to act decisively and courageously is now."
Syria earlier had struck a defiant tone, laying a record of atrocities -- rape, arson, even the destruction of Syrian culture itself -- at the feet of rebels and chiding outsiders for trying to interfere.
"This is a Syrian conflict, and it will remain as such," Foreign Minister Walid al-Moallem told the conference.
His remarks came after U.S. Secretary of State John Kerry said the path to peace had to involve the world community, and could not include Syrian President Bashar al-Assad, whom he accused of widespread human rights abuses.
"Mr. Kerry," al-Moallem said, "nobody in the world has the right to get rid of the legitimacy of a president or a constitution or a law or anything in Syria except the Syrian people themselves."
His comments were echoed by Bouthaina Shaaban, a senior adviser to al-Assad.
"Why do they decide from the Western world that Bashar al-Assad stands in the way for peace? Do we have the right to decide that any Western leader is not good for his people? Or is it the people usually who decide in every country who should be president?" she asked CNN.
"Put a mechanism for a political process after putting an end to this terrorism. And then let the Syrian people decide for themselves," Shaaban said.
The State Department later issued a statement saying that, "Instead of laying out a positive vision for the future of Syria that is diverse, inclusive and respectful of the rights of all, the Syrian regime chose inflammatory rhetoric."
"The fact remains the devastating circumstances created by the regime on the ground in Syria will not be changed by inaccurate words, they will only change through the implementation of the Geneva communique including the creation (of) a transitional governing body and by the regime taking real, concrete steps to increase humanitarian access and improve the lives of the people suffering the most," the State Department said.
The back-and-forth helped to deflate already sagging hopes that the conference will find a way to end the violence in Syria. But analysts say there is hope that progress can be made on improving the situation for the most vulnerable victims of the civil war.
The violence has claimed more than 100,000 lives since 2011. The war has become increasingly sectarian, drawing in Syria's regional neighbors and forcing out more than 2 million refugees, many of them children.
Kerry, al-Moallem and Ban joined diplomats from Russia and other world powers in Montreux to take part in the talks, which seek to set up a transitional government under a plan hashed out in Geneva in 2012 to end the conflict.
The preliminary international session started Wednesday. Direct talks between the Syrian government and opposition delegations are scheduled for Friday in Geneva.
"The solution for Syria should be made by the Syrian people inside Syria -- not in Geneva," Shaaban, the adviser to al-Assad, told CNN's "The Situation Room with Wolf Blitzer."
"We have to acknowledge that there is a huge campaign against the Syrian government for the last three years and the aim is not the Syrian government. The aim is the destruction of Syria, the destruction of the Syrian people for only the benefit of Israel. That is the true story that is happening in Syria," she said.
In his opening comments, Kerry accused the al-Assad government of using unspeakable brutality against its own people to maintain its grip on power.
"The right to lead a country does not come from torture, nor barrel bombs, nor Scud missiles," Kerry said. "It comes from the consent of the people."
His comments drew applause from Syrian National Coalition President Ahmad Jarba, who said on Twitter, "We thank Secretary Kerry for his strong comments in support of the Syrian people's struggle for freedom & dignity."
At the talks, Jarba held pictures of victims of alleged regime abuse. He made clear that the SNC, the main Syrian opposition group, sees no role for al-Assad in a transitional government.
Al-Moallem, however, blamed rebels for the atrocities, accusing them of killing and raping civilians, burning down libraries and looting artifacts from museums.
In the only specific instance he offered, he told the tale of one man who he said blew up himself and his family rather than face rebels, whom he called "the barbaric people."
"Don't be misled by the campaign of lies," he said, lashing out, over Ban's objections, at Turkey and other nations that have supported Syrian rebels.
Shaaban told CNN that Syrian authorities have not used chemical weapons.
"Chemical weapons were used by these terrorists, and we know the countries who have been helping them. It is a terrible crime what's happening against the Syrian people, and it is basically through foreign intervention," she said.
In what appeared to be a first, Syrian state television carried the speeches live -- including many derogatory references to al-Assad -- albeit with wording on the screen ridiculing the speakers or painting them as puppets acting against Syrian interests.
In a sign of the Syrian regime's disdain for the Arab League -- which suspended the regime's membership after its crackdown in 2011 -- Syrian state-run TV labeled the League's secretary-general with a scornful caption Wednesday: "Nabil Al-Arabi is speaking on behalf of the Saudi-Qatari petro-dollar that dictates him and the Arab League."
Most outside support for rebel forces has come from the Gulf monarchies of Saudi Arabia and Qatar.
'Nothing is going to be easy'
At the press conference, Kerry stressed that the Geneva communique, with its call for political transition, was the paramount focus of the summit.
"It's no secret that getting to where we are now has been difficult. Peace and stability will not arrive overnight," he said.
"But it is important that this process is now in place, it's important that the government and opposition will sit down in these next days."
He said while a sudden breakthrough should not be expected, "what we do expect is a crystallizing of the difference: Who stands for what? Who is really fighting for what? Whose arguments are based on truth? Whose arguments are based on facts?"
U.N. mediator Lakhdar Brahimi acknowledged "nothing is going to be easy" as he expressed hope both sides would meet on Friday.
The opposition and Iran
Several high-profile complications emerged even before the talks started, setting the tone for a challenging conference.
The Syrian National Coalition didn't decide until Saturday whether it would attend, finally agreeing in a vote that revealed deep divisions within its ranks.
One of the groups in the coalition blasted it for agreeing to participate in the talks, accusing it of heading to Geneva with "a folder of concessions and withdrawals."
And furor has surrounded the embarrassing public announcements by Ban, who invited -- and then disinvited -- Iran to the conference.
Iran is a key supporter of al-Assad's regime. Western leaders believe Iran has provided military and intelligence support to Syrian government forces. In addition, fighters from the Iran-backed Lebanese Shiite militia Hezbollah have seen combat in Syria on the side of the government.
The controversy over Iran threatened to derail the talks at one point.
Russian Foreign Minister Sergey Lavrov chided the United Nations on Tuesday for its abrupt U-turn on Iran, following pressure from the main Syrian opposition group and the United States.
Iran had already announced that it wouldn't be attending the peace conference because it would not tolerate any preconditions for joining the talks -- including acceptance of the framework laid out in the 2012 Geneva conference that foresees a transitional government.
Lavrov called Ban's reversal a mistake, but "not a catastrophe," adding that Russia and others will push for balanced talks between those representing al-Assad and the rebels. Moscow has been a longtime ally of the Syrian government.
He pointed out that Kerry, among others, recognized publicly that Iran is an important player in resolving the Syrian conflict.
Russian Prime Minister Dmitry Medvedev told CNN's Christiane Amanpour that the talks cannot be taken seriously without Iran involved.
"The thing that has happened with the withdrawal of the invitation to Iran, I believe that's unacceptable," Medvedev said in an exclusive interview that aired Wednesday on CNN's "Amanpour." "Can someone think the Syrian problem can be seriously discussed without the Iranian factor and their account of it?"
Besides the United States and Russia, the other permanent members of the U.N. Security Council -- Britain, France and China -- are attending the conference, along with more than 25 other countries. Representatives of the Arab League, the Organization of Islamic Cooperation and the European Union will also take part.
Al-Assad, whose forces have regained momentum against a now-fractured opposition, has said he's not looking at the talks as a way to transition out of power.
Syrian officials have talked instead about the conference as a way to arrange a cease-fire in Syria's largest city, Aleppo, with hopes of extending that truce to other parts of the country.
Al-Assad has called for the conference to include a focus on fighting "terrorism," his government's term for rebel forces.
"The war has caused horrible suffering to the Syrian people and I think that the question is why do these countries support terrorism in our country," Shaaban, al-Assad's adviser, told CNN.
"The objective is to destroy a secular, moderate beautiful example in the Arab world," she said.
In a meeting with Syria's delegates to the talks, al-Assad directed them to preserve their nation's sovereignty by "preventing and rejecting any foreign interference no matter its form and context," the state-run Syrian Arab News Agency reported Monday.
Al-Assad also said no political solution could be reached without the agreement of the Syrian people and "first and foremost the complete cessation of terrorism" and its support by other countries, the news agency said.
CNN's Jason Hanna, Marie-Louise Gumuchian, Holly Yan, Laura Smith-Spark, Ben Brumfield, Matt Smith, Chelsea J. Carter, Shirzad Bozorgmehr, Christine Theodorou, Samira Said, Becky Anderson and Nick Paton Walsh contributed to this report.