The UN political chief called Wednesday for a major international effort and bold leadership by the Israelis and Palestinians to break the political deadlock on peace talks and move ahead on an important opening by U.S. President Barack Obama.

Jeffrey Feltman told the UN Security Council on Wednesday that Obama and Secretary-General Ban Ki-moon agreed at a White House meeting on April 11 that there is "a window of opportunity" for the Israelis and Palestinians to resume peace negotiations.

He said the secretary-general reaffirmed the UN's support for "a substantive initiative" to achieve a two-state solution, including through the Quartet of Mideast mediators -- the U.S., UN, European Union and Russia.

"Now is the time for the international community to work in a concerted manner and without delay," Feltman said. "The fragile hope triggered by the renewed U.S. engagement must be sustained and translated into serious efforts by the parties."

Obama's visit to Israel and the West Bank last month led to renewed hopes of U.S. engagement, which were reinforced by three quick follow-up visits by Secretary of State John Kerry.

He has been trying to get Israeli and Palestinian leaders to agree on a new and ambitious peace process that includes reviving parts of a long-dormant plan embraced by the Arab world. The 2002 Arab Peace Initiative would have provided Israel recognition throughout the Arab world in exchange for a pullout from territory conquered in 1967.

Feltman said the secretary-general spoke of the urgency of progress and reaffirmed the UN's support for "a substantive initiative" to achieve a two-state solution at his meeting with Obama, including through the Quartet of Mideast mediators -- the U.S., UN, European Union and Russia.

In another follow-up, he said that on the sidelines of a meeting April 10, ministers from the G-8 major powers -- the U.S., Britain, Russia, Japan, Germany, France, Italy and Canada -- recommitted themselves to comprehensive peace in the Mideast and the need for a major international effort involving the Quartet and regional leaders "to drive the peace process forward." On April 28, he said, Arab leaders are sending a ministerial delegation to Washington to discuss the peace process.

Russia's UN Ambassador Vitaly Churkin told the Security Council Wednesday that Moscow is convinced a ministerial meeting of the Quartet, preferably with the involvement of Arab states, Israel and the Palestinians, could help re-launch the negotiating process. He said this "must be achieved without preconditions."

Riyad Mansour, the Palestinian UN observer, welcomed Obama's "important visit" and "the priority accorded to resolving the conflict, the renewed commitment to a just peace, and the efforts to create an atmosphere conducive for progress."

"We strongly hope that secretary Kerry succeeds in his efforts along with other regional and international partners to launch a credible peace process," he said.

But for a meaningful and successful political process, Mansour said, Israel must halt all settlement building.

"This would constitute a serious signal from Israel that it is ready to negotiate in good faith an end to the occupation," he said.

Israel must also accept the principle of withdrawal from land it seized in the 1967 war, release Palestinian political prisoners and detainees, end its "blockade" of the Gaza Strip, and allow Palestinian refugees to return, Mansour said.

Israel's UN Ambassador Ron Prosor made no mention of new settlements or the Obama visit but said peace must be built on three pillars -- education to teach Palestinians the importance of tolerance and coexistence, recognition that Israel is the nation state of the Jewish people, and security.

He added that tolerance, mutual recognition and security are also essential for Israelis and all people in the Middle East if they are to live together in peace.

Prosor accused Palestinian President Mahmoud Abbas of claiming to march toward a peaceful two-state solution while building a monument in Bethlehem depicting the boundaries of a Palestinian state which would wipe Israel off the map.