Prime Minister Benjamin Netanyahu must present a concrete plan for a two-state solution to Congress this month or face the prospect of fresh violence, J Street head Jeremy Ben Ami warned yesterday.

Ben-Ami, who directs the left-wing version of the American pro-Israel AIPAC lobby, said Netanyahu was "trying to build momentum" to stall a Palestinian plan to seek United Nations backing for statehood in September.

Open gallery view J Street’s Jeremy Ben-Ami in Jerusalem in 2010. Credit: Alon Ron

He told Reuters that he thought the only way to effectively delay the plan and reduce tensions stoked by surrounding Arab uprisings was for Netanyahu to chart a clear path to a two-state deal.

Ben-Ami said he feared Netanyahu's dismissal of reconciliation between Fatah and Hamas may only further damage already-frozen diplomacy.

"I think now in the wake of the reconciliation there's a possibility that his whole case to the Congress might be ... not putting anything on the table," Ben-Ami said.

"In our meetings here we are urging, from our perspective, that the prime minister's initiative should be a serious plan," he said, adding that he thought Israel should wait to see the policies of a new Palestinian government before condemning it.

Ben-Ami said Netanyahu ought to present a deal along lines agreed in past years of negotiations, including proposed land swaps in exchange for settlement blocs Israel would keep.

"Put a proposal on the table that meets a bar of credibility, not a provisional state on 30 or 40 percent of the land, but a real state, and let them decide if they're serious about peace or not," Ben-Ami said.

Ben-Ami said UN endorsement of a Palestinian state without Israeli agreement on borders could engender violence as the conflict continues.

"Frustration will be higher," Ben-Ami said. Such sentiment "leads to explosions and all you need is one match on the tinder and we're very worried about what that leads to."

He said Israel may itself face a global diplomatic "tsunami" including a stepped up drive for sanctions over its continued presence in the West Bank.

Netanyahu has not said what peace ideas he may broach in Washington, where he will meet U.S. President Barack Obama on May 20, ahead of his speech to Congress. Uncertainty as to what he might say has grown since his condemnation of the Palestinian unity deal signed in Cairo last week.

Israel objects to any contacts with Hamas.

Spokesmen for Netanyahu declined to comment on Ben-Ami's remarks. But an Israeli official speaking on condition of anonymity said, "I am sure that everyone who listens to the prime minister's speech in Congress will be impressed by the prime minister's desire to move forward in peace with our neighbors."