WASHINGTON (AP) — Supporters of the Iran nuclear deal are nearing the 34 Senate votes needed to keep the deal alive, preparing to deal President Barack Obama a major foreign policy victory despite intense opposition.

Sen. Bob Casey of Pennsylvania on Tuesday became the 32nd Democratic or independent senator to announce his support for the deal, and an announcement from Democratic Sen. Chris Coons was expected shortly.

"This agreement will substantially constrain the Iranian nuclear program for its duration, and compared with all realistic alternatives, it is the best option available to us at this time," Casey said in a statement.

Earlier Tuesday Sen. Ben Cardin of Maryland, top Democrat on the Foreign Relations Committee, predicted Obama would get to 34 votes by week's end. That's the number needed to uphold an Obama veto of GOP legislation aimed at blocking the deal, which will come to a vote later this month.

Republicans unanimously oppose the deal that aims to curb Iran's nuclear program in exchange for relief from economic sanctions, but critics have failed to use Congress' summer recess to turn the tide against the deal. Only two Democratic senators have come out against it.

With 34 votes looking to be in reach, supporters have begun aiming to get 41 votes, which would block the disapproval resolution from passing in the first place, and spare Obama from having to use his veto pen. Cardin, who said he remains undecided, didn't address that possibility.

In a session with students at Johns Hopkins University, Cardin discussed the pros and cons on each side and said his decision will be made on which approach is likeliest to keep Iran from becoming a nuclear weapons state. Either decision carries risks, Cardin said.

"I think it's a tough call and I sort of bristle when people say this is such an easy decision, why haven't you made it. I don't think it is an easy judgment call," Cardin said. "I think there are high risks either way."