In a speech before the UN General Assembly, U.S. President Barack Obama urged UN member states to overcome their cynicism about prospects for peace in the Middle East and support U.S.-led efforts to create and an independent Palestinian state that can coexist peacefully with Israel.
His call comes as Washington is trying to keep just-resumed talks between Israel and the Palestinians on track.
"Talks should press on until completed," Obama said. "Now is the time for the parties to help each other overcome this obstacle. Now is the time to build the trust -- and provide the time -- for substantial progress to be made. Now is the time for this opportunity to be seized."
Obama urged leaders to resist "rejectionists on both sides" who will seek to disrupt the process "with bitter words and with bombs."
And he sought to draw a line under years of failed attempts to reach agreement, saying "this time is different."
"This time we should reach for what's best within ourselves. If we do, when we come back here next year, we can have an agreement that will lead to a new member of the United Nations -- an independent, sovereign state of Palestine, living in peace with Israel," Obama said.
With Washington as mediator, Israel and the Palestinian Authority are holding the first direct talks since December 2008.
Both sides have agreed to a deadline of one year to achieve peace, and Obama said the future for each will be grim if a deal is not reached.
"If an agreement is not reached, Palestinians will never know the pride and dignity that comes with their own state, Israelis will never know the certainty and security that comes with sovereign and stable neighbors who are committed to coexistence," Obama said. "The hard realities of demography will take hold. More blood will be shed. This Holy Land will remain a symbol of our differences, instead of our common humanity. I refuse to accept that future."
Underscoring the fact that the United States is Israel's closest friend and protector, Obama said no one should question the Jewish state's right to exist.
"After 60 years in the community of nations, Israel's existence must not be a subject for debate. Israel is a sovereign state, and the historic homeland of the Jewish people," Obama said. "It should be clear to all that efforts to chip away at Israel's legitimacy will only be met by the unshakable opposition of the United States."
Palestinian Authority President Mahmud Abbas has threatened to walk out of the negotiations unless a 10-month freeze on Israeli settlement activity in the West Bank is extended.
Israel has rejected calls to extend the moratorium, which is set to expire on September 26.
However, Prime Minister Binyamin Netanyahu, who is under pressure from right-wing settler elements in his ruling coalition, has said the scope of further building in some settlements could be limited.
The other core issues include the borders of a future Palestinian state, the political status of Jerusalem, the right of return for Palestinian refugees, and Israel's security.
Obama's call for unity comes just as an investigation by the UN Human Rights Council has concluded that Israel's military acted illegally and with disproportionate levels of violence during a raid on an aid flotilla to the Gaza Strip in May that left nine people dead. The Israeli government has rejected the findings and denounced the report as "biased" against Israel.
compiled from agency and RFE/RL reports