A key Republican committee chairman acknowledged Tuesday that the White House lobbying campaign for the Iran nuclear deal has generated results, and said he doesn’t know if opponents of the deal can prevail.

The comments from Sen. Bob Corker of Tennessee, who chairs the Foreign Relations Committee and is a leading voice against the deal, came as supporters of the agreement claimed growing momentum. A 29th senator, Democrat Patty Murray of Washington, came out in favor of the deal on Tuesday.

That put supporters within reach of the 34 votes required to uphold a presidential veto of a resolution disapproving of the agreement struck by the U.S., Iran and five world powers. The deal aims to dismantle most of Iran’s nuclear program in exchange for billions in sanctions relief, but opponents say it makes perilous concessions to Iran.

Some supporters have now begun aiming to get 41 votes, which would allow Democrats to kill the disapproval resolution outright in the Senate and protect President Barack Obama from having to use his veto pen.

Corker said he didn’t know if opponents could stop that effort. But he criticized Democrats’ attempts to filibuster the disapproval resolution and block a final vote, given that Congress overwhelmingly endorsed hard-fought legislation giving lawmakers the right to weigh in on the deal.

“I find that stunning that the leader, the Democratic leader, is proposing that,” Corker told The Associated Press in a phone interview. “All but one senator voted in favor of having the right to vote on the final deal, so then to turn right around and filibuster it to me is very inconsistent and I think would be confusing to the people they represent.”

As for whether Republicans who control Congress and unanimously oppose the deal could thwart such a filibuster, Corker said: “I don’t know, I don’t know.”

“I don’t think there’s any question but the lobbying effort by the administration certainly has generated results, and I have no idea what the final vote is going to be but certainly they’ve picked up some support on the Democratic side,” Corker said.

He declined to speculate as to why lobbying by opponents, including the powerful American Israel Public Affairs Committee, has not gotten more traction. Israel says the deal poses a threat to its very existence.

In her statement backing the agreement, Murray said: “This is not a perfect deal, and there are several elements I would like to be stronger. But after working my way through the details and the alternatives, losing a lot of sleep, and having a lot of good conversations with so many people, I am convinced that moving forward with this deal is the best chance we have at a strong diplomatic solution.”

Only two Senate Democrats — New York’s Chuck Schumer and New Jersey’s Bob Menendez — have announced that they will vote against the agreement, though several key Democratic senators have yet to announce their position. One of the most-watched is Sen. Ben Cardin of Maryland, who is the top Democrat on the Foreign Relations Committee and whose position could influence colleagues.

Corker said he spoke with Cardin Tuesday morning but that Cardin remained undecided.

Congressional aides say they’ve rarely seen the White House work an issue so hard, with Obama making personal appeals to undecided lawmakers.

The disapproval resolution is certain to pass the House, though Democratic leader Nancy Pelosi has declared that Democrats have the votes to sustain an Obama veto. Two-thirds votes are required in each chamber to override a presidential veto.

(AP)