(CNN) -- Key diplomats, including U.S. Secretary of State Hillary Clinton, said Tuesday that the Syrian government's acceptance of a plan to forge peace and end violence must be more than lip service.
"Given (President Bashar) al-Assad's history of overpromising and underdelivering, that commitment must now be matched by immediate actions," Clinton said. "We will judge Assad's sincerity and seriousness by what he does, not what he says."
U.N.-Arab League envoy Kofi Annan viewed Syria's acceptance of his plan Tuesday as an "important initial step."
Annan's six-point proposal was the cornerstone of a statement endorsed last week by the U.N. Security Council.
Annan spokesman Ahmad Fawzi stressed that "implementation will be key, not only for the Syrian people, who are caught in the middle of this tragedy, but also for the region and the international community as a whole." Annan expects the Syrians to move swiftly "to put its commitments into immediate effect."
Al-Assad's regime has previously committed to end the violence that has raged since March 2011, when the government launched a fierce crackdown against protesters. The United Nations estimates that the Syrian conflict has killed more than 9,000 people; opposition activists have put the toll at more than 10,000. New clashes were reported Tuesday near the Lebanese border.
Clinton said the regime can prove its commitment by ordering its forces to stop firing and move away from populated areas, permit aid workers to come in, release political prisoners, allow unobstructed media access and begin the process of a democratic transition.
British Foreign Secretary William Hague said the plan would be "a significant first step" but only if it is "genuinely and seriously meant."
"This has not been the case with previous commitments the regime has made," he said.
German Ambassador to the U.N. Peter Wittig noted that "Syria has a history of credibility gaps." He said it "would be useful to learn in due course more about Kofi Annan's assessment of the reaction by the Syrians."
The plan calls for:
• "An inclusive Syrian-led political process" to address grass-roots grievances.
• A commitment to halt fighting and forge a U.N.-supervised halt of violence by the government and opposition groups.
• Timely humanitarian aid.
• Speeding up the release of "arbitrarily detained" people, including those engaged in "peaceful political activities."
• Ensuring "freedom of movement" for journalists.
• Respecting peaceful demonstrations and "freedom of association."
Annan has pledged to work with the Syrian opposition to ensure its part of the bloodshed ends, Clinton said.
The United States also expects steps from the opposition, she said.
"They must come forward with a unified position -- a vision, if you will, of the kind of Syria that they are working to build," Clinton said. "They must be able to clearly demonstrate a commitment to including all Syrians and protecting the rights of all Syrians."
Meanwhile, at least 79 more people were killed Tuesday, including 48 deaths in Idlib, according to the opposition Local Coordination Committees of Syria.
Clashes erupted near the Lebanese border in Homs province between the opposition Free Syrian Army and regime soldiers, the opposition network said.
Near Syria's border with Turkey, Syrian forces shot and killed two British freelance journalists Monday, opposition activists and the Committee to Protect Journalists said. Nasim Intriri and Walid Balidi, British journalists of Algerian descent, were working on a documentary, the opposition Local Coordination Committees of Syria said.
"Their deaths are yet another illustration of the grave dangers that journalists face in reporting a conflict that the Syrian government has sought to hide from the world," Mohamed Abdel Dayem, the coordinator of the committee's Middle East and North Africa program, said in a statement Tuesday.
The state-run Syrian Arab News Agency said authorities had killed and wounded members of an "armed terrorist group" Monday that were trying to infiltrate Syria from Turkey.
The Syrian government routinely blames the vaguely defined "armed terrorist groups" for violence in the country, while most reports from inside Syria suggest the government is slaughtering civilians in an attempt to wipe out dissidents.
CNN cannot independently confirm reports from inside Syria because the government severely restricts access by international journalists.
Annan has said the ongoing crisis in Syria cannot be allowed to "drag on indefinitely" but resisted setting any sort of timetable.
The former U.N. secretary-general arrived in China on Tuesday to meet with officials and rally support for his plan to end the violence.
His visit comes after a stop in Russia. Both countries have stymied U.N. Security Council attempts to take tough action again the Syrian regime, arguing the draft resolutions were not evenhanded.
Russia and China both have major trade ties with Syria. They have said they want the violence to stop and that they are not trying to protect the al-Assad regime.
Many world powers want al-Assad to step down.
But Russian President Dmitry Medvedev said that removing the president wouldn't provide a quick solution, according to Russian state-owned news agency RIA Novosti.
"The internal conflict currently tearing Syrian society apart will not disappear with the departure of one or another political figure," Medvedev said at a nuclear summit in Seoul. "To consider that Assad's departure would solve all the problems would be very nearsighted."
Russia has vetoed U.N. Security Council resolutions on Syria but has backed Annan's mission. And in an apparent hardening of Russia's position on Syria, Foreign Minister Sergey Lavrov said last week that al-Assad had handled initial peaceful protests "incorrectly."
Syrian media said Tuesday that al-Assad visited the Homs neighborhood of Baba Amr, an anti-government bastion pummeled by government security forces. For weeks, activists have reported constant shelling in parts of the city, attacks the government has attributed to terrorist groups.
The state-run Syrian Arab News Agency called al-Assad's appearance "an inspection field visit" and said the president met residents who were "agonized by heavily armed terrorist groups."
SANA said people in Baba Amr "chanted slogans of loyalty and amity" to the president.
The president urged speedy reconstruction of buildings and rehabilitation of the infrastructure. He met with some soldiers and police and praised the sacrifices and efforts of the "guardians of the homeland."
"I can't make this visit without stopping to see your accomplishments," he said. "It is your duty to defend every Syrian citizen. God willing, everything will return back to normal."
But a rebel army spokesman said Tuesday that al-Assad's regime was bracing for the worst. The rebel spokesman said Syrian authorities had banned men ages 18 to 42 from traveling abroad until they serve their compulsory military duty.
The ban "shows that the regime is preparing for the worst, and they are suffering from heavy losses from our operations and the defections all across the nation," said Lt. Riad Ahmed of the rebel Free Syrian Army. "We keep asking our brothers in the armed forces to abandon the barracks and join the revolution all over Syria, because it is a matter of time before the regime collapses."
Al-Assad's regime did not immediately issue a statement confirming or denying such a travel ban.
CNN's Saad Abedine, Ivan Watson, Arwa Damon, Elise Labott, Salma Abdelaziz, Yousuf Basil and Joe Sterling contributed to this report.