Sharp differences within the Israeli government over peace negotiations played out in the unusual setting of the United Nations General Assembly on Tuesday, with Foreign Minister Avigdor Lieberman using the podium to say that peace with the Palestinians required an intermediate agreement lasting “decades” and that the issue of Iranian belligerence should be addressed first.

Mr. Lieberman’s position contradicted the goal adopted by Prime Minister Benjamin Netanyahu, and the position of the Obama administration, that direct negotiations — which resumed this month — be used to resolve the most knotty problems within a year. Mr. Netanyahu’s office quickly issued a statement disowning the remarks.

Mr. Lieberman, no stranger to generating controversy, used Israel’s address to the annual General Assembly to push the idea that given various emotional and practical problems, neither side was ready for peace.

“The emotional problems are, first and foremost, the utter lack of confidence between the sides and issues such as Jerusalem, recognition of Israel as the nation-state of the Jewish people and refugees,” he said, his remarks prompting the two-member Palestinian delegation to leave the hall. “Under these conditions, we should focus on coming up with a long-term intermediate agreement, something that could take a few decades.”

The guiding principle must not be “land for peace, but rather exchange of populated territory,” which he said meant “moving borders to better reflect demographic realities.” Mr. Lieberman has long advocated minimizing the number of Israeli Arab citizens.

On Iran, some foreign policy experts argue that an Israeli-Palestinian peace deal will help neutralize Iranian influence among Arabs, especially given that the Palestinian issue has never had much emotional resonance among Iran’s overwhelmingly Shiite Muslim population; the main holy cities for Shiites include Karbala and Najaf but not Jerusalem.

Mr. Lieberman argued that it should be the reverse, that Iranian support for groups seeking to attack Israel, like Hamas and Hezbollah, should be undermined before any peace deal is likely to succeed.

Mr. Lieberman, himself a West Bank settler and leader of the ultranationalist Yisrael Beiteinu party, rejected the argument that settlements were thwarting peace. Direct negotiations hang in the balance this week because the Palestinian president, Mahmoud Abbas, has threatened to walk away to protest the end last Sunday of a 10-month Israeli moratorium on settlement construction.

The Arab League is scheduled to discuss the issue on Monday, and the Syrian foreign minister, Walid al-Moallem, used his United Nations speech on Tuesday to lay down the likely hard-line Arab position. “Relentless settlement activities are about to make this two-state solution a dead letter,” said Mr. Moallem, while repeating Syria’s willingness to reopen indirect peace talks with Israel via Turkey.

Mr. Lieberman began his speech by taking a swipe at Israeli leaders from Yitzhak Rabin to Ehud Olmert, saying they all failed to achieve peace because they approached it the wrong way. He included the current prime minister on that list.

“The content of the foreign minister’s speech at the United Nations was not coordinated with the prime minister,” read the short statement from Mr. Netanyahu’s office. “Prime Minister Netanyahu is the one who is managing the political negotiations of the State of Israel.”

At the State Department, the spokesman, Philip J. Crowley, said he would leave the reaction to Mr. Netanyahu. “The prime minister told us that there are difficult politics on his side, and this is perhaps a manifestation of that,” Mr. Crowley said at a briefing.