BALTIMORE (AP) -- A key Democrat predicted Tuesday that there will be enough votes in the Senate by week's end to uphold an expected veto by President Barack Obama of a resolution disapproving the Iran nuclear deal.

Sen. Ben Cardin of Maryland, the top Democrat on the Foreign Relations Committee, told students at Johns Hopkins University that he remains undecided. But he said the numbers are close to favoring the president when Congress votes later this month on GOP legislation disapproving of the deal.

Republicans unanimously oppose the deal that aims to curb Iran's nuclear program in exchange for relief from economic sanctions. As of now 31 Democratic and independent senators have announced support for the agreement, just three shy of the number needed to uphold Obama's veto.

"The numbers in Congress are looking pretty close to favoring the president," Cardin told students in a detailed question-and-answer session on the issue. "The president will have at least 32 committed Democrats on his side by the end of the day. That number looks like it will clearly get to the 34 number by the end of the week so it looks pretty clear the president is going to have the support to sustain a veto."

Cardin didn't name names, but Democratic Sen. Chris Coons of Delaware has scheduled a speech to address the issue later Tuesday.

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 didn't address that possibility.

He 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."

By AP