Calling Washington’s ties to Israel “unshakable,” Vice President Joseph R. Biden Jr. opened talks with Israeli leaders on Tuesday, part of a concerted American effort to restart Israeli-Palestinian peace talks and keep Israel focused on sanctions against Iran’s nuclear program rather than unilateral military action.

Vice President Joseph R. Biden Jr. spoke in Jerusalem on Tuesday.
On a five-day visit to the Middle East, Mr. Biden is also expected to meet Palestinian and Jordanian leaders and give a speech at Tel Aviv University expressing American solidarity with Israel — a theme that was apparent from the beginning of his discussions here.

Mr. Biden met Tuesday with President Shimon Peres and wrote in a guestbook at the president’s residence that “the bond between our two nations has been and will remain unshakable. Only together can we achieve lasting peace in the region.”

In a conversation with Mr. Peres in front of reporters, Mr. Biden reinforced the point, saying: “There is absolutely no space between the United States and Israel in terms of Israel’s security. None.”

Mr. Biden later met with Prime Minister Benjamin Netanyahu. George J. Mitchell, the administration’s Middle East envoy, announced Monday in Jerusalem that, as expected, Israel and the Palestinians had agreed to start indirect negotiations and that he would be back next week to continue structuring those talks.

They will be the first peace talks in more than a year between the sides, but they have generated only the faintest enthusiasm here. Israeli and Palestinian leaders are skeptical that the other side will really accept a two-state solution. In addition, the contours and powers of a future Palestinian state are in sharp dispute.

Saeb Erekat, the Palestinians’ chief negotiator, told Israel’s Army Radio that this seemed likely to be the last chance to achieve two states and indicated that if the effort failed, there would be no choice but to insist that Israelis and Palestinians share one state.

Mr. Erekat added that the Palestinians were prepared to see a small percentage of West Bank territory stay in Israeli hands to accommodate settlements built after the area was conquered by Israel in the 1967 war, but only on the condition that Israel yield an equal amount of land in compensation.

“I’m not saying the borders of ’67; I’m saying the size of ’67,” he said.

Mr. Netanyahu supports two states but wants the Palestinian side to be demilitarized and to accept an Israeli military presence on its future eastern border to prevent the import of weapons and rockets that could be aimed at Israel’s population centers.

The issue of Israeli settlements in the West Bank and of Jewish residents in East Jerusalem is also expected to be a source of great contention. There are 500,000 Israeli Jews living on land the Palestinians want as part of their state. Even if much of the land they are on were granted to Israeli annexation in exchange for territory for the Palestinians, there would still be a need to relocate tens of thousands of settlers.

Israel announced a 10-month partial freeze on settlement building in November but allowed the completion of about 3,000 units already started and excluded Jerusalem from the moratorium, meaning that construction has not really slowed.

On Monday, as Mr. Biden was heading into the country, the Defense Ministry announced permission for 112 more units in an ultra-Orthodox settlement, Beitar Illit, saying that there were “safety” reasons for the exception and that the units had been approved before the moratorium was announced. The Palestinian leadership condemned the move as Israeli hypocrisy.

A full construction freeze in settlements has been a Palestinian condition for renewing direct talks, and Palestinian leaders say it remains their condition to move from these indirect talks to direct ones.

The coming negotiations are expected to last some months and are being called “proximity talks,” meaning that Israeli and Palestinian leaders will not sit at the same table but will respond to proposals carried by American officials between Jerusalem and the Palestinian leadership’s headquarters in Ramallah, in the West Bank. After thousands of hours of direct talks in past years, this is a sign of how much relations have deteriorated.

Much of Mr. Biden’s attention will be on Iran and assuring Israel that its fear of an Iranian nuclear weapons program is shared by the Obama administration and most of the world. Iran insists that its nuclear program is for peaceful purposes, but few Western governments believe it.

“I can promise the nation of Israel that we will meet, as allies, any security challenge that we may face,” Mr. Biden told the Israeli newspaper Yediot Aharonot in written answers to questions published on Monday. “Iran equipped with nuclear weapons will constitute a threat not only to Israel, but also to the United States.

“Iran’s obtaining nuclear arms will deeply undermine the stability of the entire international community and could lead to a nuclear arms race in the Middle East that will be extremely dangerous for everyone involved, including to Iran. For this reason, our administration is mobilizing the international community to insist that Iran fulfill its international commitments. If it does not, it will have to deal with serious consequences and with increasing isolation.”

Israel feels that its risk from an Iranian nuclear weapon is greater than almost anyone else’s, given its proximity and the ideology of the Iranian leadership, which calls for the end of the Jewish state, arms Hezbollah in Lebanon and Hamas in Gaza, groups that oppose the existence of Israel, and frequently denies the reality of the Holocaust.

Israel has been training for a military attack on Iran’s nuclear facilities, but Washington has been pressing it to hold off and help work out a sanctions regime. The chairman of the Joint Chiefs of Staff, the director of the C.I.A. and the national security adviser have all been here with that message. Mr. Biden is expected to say the same.