US President Barack Obama has accused the Israel lobby of spending millions of dollars to spread false claims about the Iran nuclear agreement, and vowed to push back, according to a report.

At a meeting this week, Obama told leaders of the American Israel Public Affairs Committee (AIPAC), the most powerful pro-Israel group in the United States, that he would counter their efforts to sink the nuclear agreement with Iran, The New York Times reports, citing people present at the gathering.

“Mr. Obama told the AIPAC leaders that he intended to hit back hard,” the report said.

The next day, Obama criticized the opponents of the July 14 agreement as “lobbyists” spending millions of dollars to disseminate the same hawkish rhetoric that led to the US invasion of Iraq in 2003.

“Many of the same people who argued for the war in Iraq are now making the case against the Iran nuclear deal,” he said during a speech at American University in Washington on Wednesday. “More than a decade later, we still live with the consequences of the decision to invade Iraq.”

Although Obama never mentioned AIPAC by name, his remarks reflected a new low in relations between the most potent pro-Israel lobbying group in Washington and an acting American president.

“It’s somewhat dangerous, because there’s a kind of a dog whistle here that some people are going to hear as ‘it’s time to go after people,’ and not just rhetorically,” said David Makovsky, a former Middle East adviser for the Obama administration. “There’s almost a bunker mentality on both sides.”

Obama has launched an aggressive campaign of private entreaties and public advocacy to rally enough Democratic support to preserve the nuclear agreement ahead of a September vote on it in the Republican-led Congress.

Most Republicans oppose the nuclear agreement with Iran, but they need a two-thirds vote in both chambers of Congress to override a presidential veto, and to reach that threshold, Republicans need Democratic support.

Israeli Prime Minister Benjamin Netanyahu addresses the AIPAC policy conference in Washington, DC, on March 2, 2015. (AFP photo)

AIPAC is spending about $40 million to run TV advertisements in 35 states urging legislators to vote down the accord, and is leaning hard on Democrats.

Nearly 60 legislators--22 Democrats and 36 Republicans-- from the US House of Representatives will travel to Israel this month, which is being paid for by the American Israel Education Foundation, the charitable arm of AIPAC.

In a major break with the White House, Senator Chuck Schumer, an influential Jewish Democrat from New York, announced Thursday that he would vote against the nuclear agreement with Iran.

Sen. Schumer talks with a staff member after the weekly Democratic policy luncheon at the US Capitol on August 4, 2015. (AFP photo)

Moments after Schumer’s announcement, Representative Eliot Engel, the ranking Democrat on the House Foreign Affairs Committee, also declared that he would join Obama’s rivals to oppose the nuclear accord.

Another House Democrat, Rep. Brad Sherman of California, defected from the Obama administration Friday over the Iran agreement.