(CNN) -- In back-to-back speeches Tuesday to the U.N. General Assembly, Israeli Prime Minister Benjamin Netanyahu accused the Iranian president, Hassan Rouhani, of seeking to obtain a nuclear weapon, and the Iranian representative insisted that Tehran's nuclear program was intended solely for peaceful purposes.
Rouhani, whose demeanor has been more moderate than that of his predecessor since he took office in August, is "a wolf in sheep's clothing, a wolf who thinks he can pull the wool over the eyes of the international community," Netanyahu said.
Western leaders have expressed optimism about Iran's more moderate tone under Rouhani, whose recent comments have raised hopes that a deal could be struck over the Middle Eastern nation's nuclear program.
But Netanyahu urged world leaders not to be duped by Rouhani, calling him a "loyal servant" to the Islamic regime, which he said "executes political dissidents by the hundreds" and jails them by the thousands.
"It's not hard to find evidence that Iran has a nuclear weapons program," Netanyahu said. "It's hard to find evidence that Iran doesn't have a nuclear weapons program."
Netanyahu said that even since Rouhani assumed office, "this vast and feverish effort has continued unabated."
Rouhani "thinks he can have his yellowcake and eat it, too," Netanyahu said in a reference to the raw uranium ore that can be processed into nuclear weapons.
International sanctions have left Iran "on the ropes," the Israeli prime minister told the world body, whose Iranian representative was not present. He called for the sanctions to remain in place to force Iran to halt its nuclear aspirations.
"We all want to give diplomacy with Iran a chance to succeed," he said. "But when it comes to Iran, the greater the pressure, the greater the chance."
But the Iranian representative rejected Netanyahu's accusations, calling them "inflammatory" and "unfounded."
Iran "has an inalienable right to peaceful nuclear energy" and is fully committed to its nonproliferation obligations," said Khodadad Seifi, counselor for Iran's U.N. mission.
"All Iranian nuclear activities are -- and have always been -- exclusively for peaceful purposes," he said, adding that Tehran is cooperating with the U.N.'s nuclear watchdog, the International Atomic Energy Agency, and that its work is carried out under surveillance cameras.
"There is no single acceptable reason to possess nuclear weapons, but there are many agreeable reasons to abolish them all," he said.
He called further for "respectful" negotiations. "Iran stands ready to ensure that its nuclear program will continue to remain exclusively peaceful," he said.
Seifi also called for the international community to annul the sanctions that have crippled the nation's economy.
And he noted that Israel, unlike Iran, has not signed the nonproliferation treaty. "Israel is the only one in the region that possesses all types of weapons of mass destruction but is not party to any of the treaties banning them," he said.
And he warned Netanyahu that Tehran is capable of defending itself if Jerusalem's war of words goes beyond vitriol. "The prime minister had better not even think about attacking Iran, let alone planning for that," he said.
Netanyahu's comments drew a sharp response from Mustafa Barghouti, a member of the Palestinian Liberation Organization's Central Council and head of an independent political party.
"Why does he forget to speak about the facts and also ignores the facts that Israel is also a nuclear power and the way to peace in the Middle East is to make it a free nuclear zone?" he asked.
Tuesday's repartee came a day after U.S. President Barack Obama met with Netanyahu in the White House and a few days after he spoke with Rouhani by telephone in the first such direct contact between the nations' leaders since the Iranian revolution in 1979.
On Monday, Obama said he has a "good working relationship" with Netanyahu, and reaffirmed the U.S. bond with the Israeli people.
"Our unshakeable bond with the Israel people is stronger than ever," he said. "Our commitment to Israel's security is stronger than ever."
Both leaders said Iran was a key topic.
"Iran is committed to Israel's destruction, so for Israel, the ultimate test of a future agreement with Iran is whether or not Iran dismantles its military nuclear program," Netanyahu said. "That's the bottom line."
Obama said that if Iran wants sanctions relief, it will have to meet "the highest standards of verifications."
"It is absolutely clear that words are not sufficient," Obama said on Monday. "We have to have actions that give the international community confidence that, in fact, they are meeting their international obligations fully and that they are not in a position to have a nuclear weapon."
In the latest indication of Tehran's new approach to Washington, Iran's semi-official Fars News Agency reported that Rouhani wants to establish direct flights between Iran and the United States.
And in the latest indication of Iran's continuing problems with Israel, the Israeli government said over the weekend that it had arrested an Iranian-born man and accused him of spying for Tehran.
According to the Israeli government, the alleged spy was carrying photos of various sites, including the U.S. Embassy in Tel Aviv.
On Tuesday, the Iranian news agency cited a Foreign Ministry spokeswoman who rejected the assertion as "baseless."