A Washington conference hosted this week by a new liberal Jewish advocacy group has sparked a diplomatic row and proxy battle over the Obama administration's stance on Israel at a time of simmering tensions between Washington and Israel's right-leaning government.

J Street, an advocacy and lobbying firm created 18 months ago, is holding its first annual conference beginning Sunday, with participation from about 150 Democratic members of Congress, many current and former Israeli politicians and U.S. national security adviser James L. Jones, who will be giving a keynote speech Tuesday.

But the self-described "pro-Israel, pro-peace" group has been rebuffed in its attempts to get Israel's U.S. ambassador, Michael Oren, to speak at the gathering. In a statement explaining the refusal, the Israeli Embassy accused J Street of endorsing policies that "could impair Israel's interests."

The organization also abruptly canceled plans for a "poetry slam" at the event after conservative activists and bloggers unearthed writings by two participants that compared the suffering of Holocaust victims to that of Palestinians in Israel's occupied territories. In addition, at least 10 members of Congress, including Republicans, canceled participation in the conference under pressure from conservative critics, according to J Street and legislative aides.

The skirmishing comes at a time of ongoing tensions between President Obama, who has vowed to restart Mideast peace talks by year's end, and the government of Israeli Prime Minister Binyamin Netanyahu, who has resisted U.S. demands to halt settlement construction in the West Bank and take other steps in advance of negotiations.

The furor also underscores unhappiness among some long-established Jewish groups that believe the Obama administration has snubbed their concerns about the Middle East conflict. The administration has made a point of meeting with a wide range of groups on the topic; Jones recently spoke to the American Task Force on Palestine, while Obama is scheduled to address the Jewish Federations of North America next month.

Tommy Vietor, an administration spokesman, said "the White House always welcomes the opportunity to discuss the president's views and engage in a dialogue with interested parties."

J Street was formed on the theory that existing U.S. Jewish groups, including the influential American Israel Public Affairs Committee (AIPAC), lean too far to the right compared with the views of American Jews. J Street has garnered controversy for many of its positions, including opposing immediate sanctions on Iran and criticizing Israel's incursion into Gaza as "disproportionate."

J Street's executive director, Jeremy Ben-Ami, said many of the group's positions dovetail with those taken by Obama, who remains highly popular among Jews in the United States. He said the group has been the victim of "thuggish smears" by conservatives who favor more hawkish policies in the Israeli-Palestinian dispute, and said he had hoped that Oren would have accepted an invitation to speak at the conference.

"I am extremely disappointed that this is the reaction of the government of Israel to an organization that is looking to expand the base of support in this country for Israel and is deeply concerned about its future," Ben-Ami said.

The conference and its scheduled participants set off criticism from conservatives such as Weekly Standard blogger Michael Goldfarb, a former adviser to the presidential campaign of Sen. John McCain (R-Ariz.). Goldfarb referred to the conference as an "anti-Israel bash" and raised questions about the poetry event before it was canceled.

Some conservatives have also criticized J Street for accepting donations from individuals connected to organizations doing Palestinian and Iranian advocacy work. In addition, conservatives have attacked the conference for including Salam al-Marayati, founder of the Muslim Public Affairs Council, who apologized in 2001 for suggesting on a radio show that Israel should be considered a suspect in the Sept. 11 attacks.

StandWithUs, a Los Angeles-based Jewish advocacy group, has taken out newspaper ads this month criticizing J Street and faxed a "statement of concern" about the group to members of Congress listed as hosts of the conference. At least 10 lawmakers, including House Republican and likely senatorial candidate Michael N. Castle (Del.), dropped off the schedule amid the complaints.

Roberta Seid, research and education director for StandWithUs, said she views J Street as "outside the mainstream," and that broad support for Obama among American Jews does not mean agreement with the administration's Israel policy.

"American Jews seem to love Obama; American Jews are liberal," Seid said. "But they are much firmer in their support of Israel and opposed to viewing the conflict as equally Israel's fault. I think they draw the line there."

But Jon B. Alterman, director of the Middle East program at the centrist Center for Strategic and International Studies, said many critics are missing what the White House and State Department are attempting to achieve by addressing multiple groups in the Middle East conflict.

"I don't see this as the Obama administration choosing one approach or the other; I see the Obama administration as engaging broadly," said Alterman, who is scheduled to be a panelist at the J Street conference. "There's a broad effort to speak to diverse audiences about the president's level of engagement and his desire to move this process forward."