WASHINGTON - Some four dozen former top U.S. diplomats and prominent policy analysts are urging President Barack Obama not to veto a proposed U.N. Security Council resolution that is expected to reaffirm the illegality of Jewish settlements in the Occupied Territories.

In a letter released here Wednesday, former U.S. ambassadors to Israel, as well as other former senior Middle East policy-makers, warned that "America's credibility" in the region will be at stake when the resolution is finally presented for a vote, probably some time next month.

"At this critical juncture, how the US chooses to cast its vote on a settlements resolution will have a defining effect on our standing as a broker in Middle East peace," asserted the letter, which was signed by among other diplomatic luminaries, former UN Amb. Thomas Pickering and former Defense Secretary Frank Carlucci.

"But the impact of this vote will be felt well beyond the arena of Israeli-Palestinian deal-making - our seriousness as a guarantor of international law and international legitimacy is at stake," it went on.

"America's credibility in a crucial region of the world is on the line - a region in which hundreds of thousands of our troops are deployed and where we face the greatest threats and challenges to our security. This vote is an American national security interest vote par excellence. We urge you to do the right thing," it concluded.

The letter, which featured signers from both Democratic and Republican administrations, as well as former career foreign service and intelligence officers, comes amid what appears to be disarray among current U.S. Mideast policy-makers in the wake of last month's collapse of their efforts to persuade the Israeli government to agree to a three-month partial moratorium on settlement activity on the West Bank.

The administration had hoped that Israel's agreement - in exchange for billions of dollars worth of new warplanes, various security guarantees, and a pledge to veto any Security Council resolution critical of Israel over the next year - would help coax the Palestine Authority (PA) President Mahmoud Abbas to revive direct peace talks which broke off last September when an earlier, 10-month partial settlement moratorium expired.

Settlement construction on the West Bank and the demolition of Palestinian property in East Jerusalem have increased sharply since then, according to the United Nations and Israeli and Palestinian human rights monitors.

Abbas has refused to return to direct talks unless Israel freezes all settlement activity in the Occupied Territories, including in East Jerusalem. The Obama administration made a similar demand of Netanyahu last year but was rebuffed in what many analysts here and in the Middle East have characterized as a major blow to Washington's credibility throughout the region.

While Obama's Special Envoy for Middle East peace, George Mitchell, struggles to keep proximity talks between the two parties alive, the Palestinians and their allies are currently floating a draft Security Council resolution that condemns the settlements as illegal under international law and an obstacle to peace.

The resolution is part of a larger diplomatic effort that also includes gaining formal international recognition for a Palestinian state based on the pre-1967 war Green Line. That effort has scored some significant successes in recent weeks, as a number of Latin American states, led by Brazil, have granted such recognition, while key members of the European Union (EU) have upgraded their diplomatic relations with the PA or are considering doing so.

The administration has indicated its opposition to all such moves, although it permitted the Palestine Liberation Organization (PLO) for the first time to hoist the Palestinian flag outside its office here.

Even that move, however, elicited harsh criticism from the so-called "Israel lobby" here and its supporters in Congress, notably the new Republican chair of the House Foreign Affairs Committee, Florida Rep. Ileana Ros-Lehtinen.

"Raising this flag in [the District of Columbia] is part of the Palestinian leadership's scheme to manipulate international acceptance and diplomatic recognition of a yet-to-be-created Palestinian state while refusing to directly negotiate with Israel or accept the existence of Israel as a democratic, Jewish state," she complained.

Ros-Lehtinen, whose top individual campaign contributor, Irving Moskowitz, is a major funder of the most militant settlements in the West Bank and East Jerusalem, also condemned the PA's proposed Security Council resolution as "part of the same strategy aimed at extracting concessions without being required to meet international commitments."

With respect to that resolution, the Obama administration now appears to find itself between a rock - the new Republican and pro-Likud majority in the House of Representatives, as well as most Democratic lawmakers who are wary of crossing the Israel lobby - and a hard place - fast-growing international support, including from its most important European allies, for the creation of a Palestinian state, as well as Washington's own credibility as a good- faith mediator in the Israeli-Palestinian conflict.

Virtually all the world's nations and the World Court have regarded Israeli settlements in territory conquered during the 1967 war as illegal under the Fourth Geneva Convention.

A 1978 State Department legal opinion agreed with that assessment, holding that the settlements were "inconsistent with international law", an assessment that, despite former President Ronald Reagan's assertion that they weren't "illegal" during a 1981 press conference, has never been repudiated or revised.

Nonetheless, when asked publicly about the settlements' legality, Washington officials since Reagan have generally declined to answer the question directly, insisting instead that they were an "obstacle to peace" or were "unhelpful".

That practice has continued under Obama who, however, declared in his widely-hailed June 2009 address in Cairo that Washington did not accept the "legitimacy" of continued Israeli settlement activity.

The administration's discomfort with being confronted squarely with the question of legality was evident Tuesday when reporters grilled State Department spokesman P.J. Crowley on whether the administration would veto the resolution.

Aside from insisting that "our position on settlements is well known", he indicated that the administration opposed bringing the resolution to the Council and that "these issues should be resolved ...through direct negotiations."

But the letter, which was initially published by Steve Clemons, the director of the American Strategy program on his widely read thewashingtonnote.com website, stressed that the administration's waffling on the issue should end.

"The time has come for a clear signal from the United States to the parties and to the broader international community that the United States can and will approach the conflict with the objectivity, consistency and respect for international law required if it is to play a constructive role in the conflict's resolution," it said. "[D]eploying a veto would severely undermine US credibility and interests, placing us firmly outside the international consensus, and further diminishing our ability to mediate this conflict."

Besides Pickering, who served at the U.N. under George H.W. Bush and Carlucci, Reagan's national security adviser and defense secretary, signatories several former ambassadors to Israel, including Pickering himself, William Harrop, and Edward "Ned" Walker.

Other signers included former assistant secretaries for Near East affairs under Reagan, Richard Murphy and Nicholas Veliotes, as well as several other assistant secretaries and deputy assistant secretaries who served in other administrations.

Jim Lobe's blog on U.S. foreign policy can be read at http://www.lobelog.com.