WASHINGTON –Sen. Cory Booker (D., N.J.) will support the international nuclear deal with Iran, he said Thursday, adding to the growing momentum for the agreement despite intense pressure from critics, and his own reservations.

Booker announced his stand in a lengthy statement full of concern about the international pact and worry about its impact on Israel, but said he concluded that supporting the deal is the best way to deter Iran for now and maintain a united international front.

"We have now passed a point of no return that we should have never reached, leaving our nation to choose between two imperfect, dangerous and uncertain options," Booker's statement said. "Left with these two choices, I nonetheless believe it is better to support a deeply flawed deal, for the alternative is worse."

He added, "the United States must recognize that to make this deal work, we must be more vigilant than ever in fighting Iranian aggression."

Booker's stand comes one day after President Obama secured the 34th Senate vote in favor of the agreement, ensuring that it would survive Congressional opposition from Republicans and some Democrats. Booker could have voted against the plan and likely seen it enacted anyway.

But Obama is still hoping to win at least 41 Senate votes to block a plan to kill the deal – a result that would spare him the symbolic hit of having Congress pass a resolution disapproving one of his most significant international achievements. Booker is the 35th senator to support the pact, one more than Obama needs to uphold a veto blocking the resolution of disapproval. Two more announced their support shortly after Booker.

New Jersey's senior senator, Bob Menendez, is one of just two Democratic senators to oppose the plan, and Booker had come under significant pressure from Gov. Christie and some Jewish groups to vote against it. The American Israel Public Affairs Committee has a rally planned for Thursday night in North Jersey to pressure Booker, with former Connecticut Sen. Joseph Lieberman slated to lead the event. Millions have been poured into television advertising to try to sway lawmakers, particularly Democrats from the northeast, who were seen as potential 'no' votes despite Obama's push for the deal.

Booker has forged close ties to the Jewish community: he was once president of a Jewish student group at Oxford, sometimes sprinkles his speeches with Yiddish and has spoken out forcefully on the Senate floor in defense of Israel. He received significant backing from Jewish groups when he ran for Senate.

In a statement that ran to nearly 3,500 words and that he posted on Medium, he lamented that the deal will not fully dismantle Iran's nuclear facilities, but concluded that it is worth the risk because it will delay Tehran's push for a nuclear weapon and give the international community a better chance to monitor Iranian acitivity.

Like many other senators -- including Sens. Bob Casey (D., Pa.) and Chris Coons (D., Del.) on Tuesday -- he backed the deal despite expressing significant concern about its details, spending much of his analysis delving into weaknesses. His objections went so far that a spokesman for Senate Majority Leader Mitch McConnell, the chamber's top Republican, promoted Booker's analysis on Twitter.

Rabbi Shmuley Boteach, an outspoken critic of the deal who described Booker as a "soul friend," called the senator's decision "troubling and tragic."

"His statement of support is riddled with logical inconsistencies," Boteach said in a news release, calling it astonishing that Booker would describe so many problems and then embrace the deal.

But, like other Democrats who had been on the fence, Booker said he saw no realistic alternative, and worried about the impact on U.S. credibility if Congress killed an agreement negotiated with five international partners: the United Kingdom, France, China, Germany and Russia. Breaking with those countries, Booker concluded, would isolate the U.S. and allow Iran to gain steam as others roll back their sanctions.

"The reality is that rejecting the deal leads to a world in which a better deal is highly improbable, sanctions are greatly reduced in strength, the Iranian economy picks up some steam, and few if any of the benefits of the deal are in place," Booker wrote. "We need to be honest about our choices – they are bad – and pursue the path that is more likely to provide security for the United States and its allies and best prevents Iran from obtaining a nuclear weapon."

He called the deal "an effective framework for preventing Iran from obtaining a nuclear weapon in the near-term, provided we are willing to address infractions – however small they are – with meaningful actions immediately when they occur."

But he still worried about Iran's threat to Israel, and wrote at length about conversations with people whose family members survived or died in the Holocaust.

"I am united with all who are determined to ensure that we never again see genocide in the world. That means not allowing Iran to ever obtain a nuclear weapon, period, regardless of what it takes," Booker said, calling on stern U.S. vigilance once the deal goes into effect.

Booker joins most Philadelphia-area Democrats in backing the deal, including Casey, Coons and Tom Carper of Delaware.

Sen. Pat Toomey (R., Pa.), the region's only Republican senator, opposes the agreement.

This story has been updated with additional detail.

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