On the street map of Washington DC there is a strange omission. Most streets are designated by either a number or a letter. But look as hard as you want there is no J Street. Seemingly, a hand-written capital I or J were seen as being too similar; a recipe for confusion.

This exception is seen by the head of the new liberal and decidedly dovish Israeli lobby group in Washington as a useful metaphor. "Just as there is no J Street on the grid in Washington DC," says Jeremy Ben Ami, J Street's Executive Director, his organisation "is looking to fill a similar gap in the political map".

met Mr Ben Ami three floors below ground level in the sub-basement of the Grand Hyatt hotel. J Street's first national conference was in full swing around us. But there was no bunker mentality here. It was more of a coming out party.

J Street's goal was to give a voice to a "broad segment of the American Jewish community and other friends of Israel who believe that peace and an end to the conflict is essential for Israel's security and survival".

"There was a real sense of urgency," he said, a fear that time was running out for a two-state solution - for the idea of two countries, Israel and Palestine, living peacefully, side-by-side.

"This president and this presidency may be the last opportunity to bring about that two-state solution," he asserted.

The victory of Barack Obama has been crucial to the emergence of this new lobbying effort. The liberal wing of the Jewish community feels emboldened and listened to. A clear sign was the fact that the keynote speaker at this conference was General James Jones, the US National Security Advisor.

'Absent values'

He drew rapturous applause when he told the audience that he was happy to be there and that this administration would be present at all future J Street conferences.

Interestingly Israel's ambassador to Washington refused an invitation to attend. The Israeli Embassy here put out a statement saying that it had privately communicated "its concerns over certain policies of the organization that may impair the interests of Israel". Nonetheless it would send an observer.

"I think it is a serious mistake on his part and on the part of the government of Israel," said Mr Ben Ami. "We are representative of a very significant part of the American Jewish community."

Opinion in Israel seems divided though; Israeli opposition leader Tzipi Livni and President Shimon Peres both both sent J Street warm messages of support.

However, J Street is a newly spawned minnow in a sea dominated by a much bigger fish - the long-established American Israel Public Affairs Committee (Aipac) which in recent years has been very close to the Bush administration. Even Aipac's enemies admire its organisational and lobbying skills, though some of its more strident critics have argued that it is distorting US foreign policy in favour of Israel.

Jeremy Ben Ami says he admires some elements of the existing pro-Israeli lobby's work. He says that J Street is not there to take on Aipac. "We are looking to give a positive voice to a message and a set of values that have been absent in American politics and in the Jewish community for too long," he said.

J J Goldberg, executive editor of the New York Jewish newspaper The Forward, believes that J Street's primary impact may be to moderate the existing lobby: "If J Street is effective, it will pull Aipac to the left as well. It will balance out the right-wing pressures."

He too stressed the importance of J Street's emergence for the Obama Administration: "When they [the administration] take a move that is going to be hard for Israel, they will have people saying to the Jewish community, credibly - no, this makes sense, hold your breath - this is going to work out."

Fundamental change

There was a strong congressional presence at this conference, though few of the stars from Capitol Hill. American-Arab organisations who share J Street's emphasis on a two-state solution were involved and the Jordanian Ambassador also spoke.

But there were critics. Outside a handful of demonstrators waved placards - one saying "J Street Nazis". I asked its holder, an elderly Jewish man from Florida, how he justified this message? "J Street are Jews who have sold-out, who didn't really support a Jewish State," he said.

"J-Street told us that the Jewish community could trust Obama," he went on. "Well, they were wrong and can not therefore be trusted."

It's a view shared by many more conservative American Jews. The Jewish blogosphere and right-wing pundits have been in over-drive condemning J Street.

But Jeremy Ben Ami says that this conference has been vastly more successful than he had hoped. In many ways J Street is trying to resolve the paradox that in recent years the Jewish community's representative bodies have been much more conservative on issues concerning Israel than the vast majority of US Jews who voted overwhelmingly for Barack Obama.

J Street believes that if the US is truly to recalibrate or shift its policy on the Middle East, then first there has to be a fundamental change in the terms of the debate at home.