One of the most influential pro-Israel lobbies in Washington has begun urging lawmakers to vote down the yet-unfinished final nuclear deal between Iran and world powers, Bloomberg reported on Wednesday.

“[The American Israel Public Affairs Committee] is now prepared to fight the White House by pushing Democrats to vote against the president’s signature second-term foreign policy initiative,” said the report.

One AIPAC mailing being circulated was a letter to Rep. Debbie Wasserman Schultz (D-FL) urging her “to play a role in ensuring that Congress does not accept a deal that does not eliminate the Iranian pathway to a nuclear weapon.”

Persuading lawmakers to challenge a U.S. president’s foreign policy represented a break from AIPAC’s usual lobbying efforts, which apparently proved more or less successful as negotiations over the Iran deal progressed, the Bloomberg report said.

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But because of concerns that the Iran deal is shaping up to look more like recent statements being made by Iranian Supreme Leader Ayatollah Khamenei, AIPAC and other pro-Israel groups have begun focusing their efforts on an upcoming vote in congress that could veto President Barack Obama’s ability to waive sanctions.

The report was published as Khamenei refuted the last of AIPAC and other pro-Israel groups’ demands for a comprehensive nuclear deal with Iran, shunning more comprehensive inspections of Iranian military sites and refusing to freeze sensitive nuclear work.

Other demands made by these pro-Israel groups were phased-out sanctions relief, the dismantlement of Iran’s nuclear infrastructure and addressing the possible military dimensions of its program, all of which have come into question over the last several weeks whether by media reports, or statements by U.S. or Iranian officials.