Senate Majority Leader Mitch McConnell of Kentucky and other congressional leaders expressed doubts Sunday about a historic agreement with Iran to address that country’s nuclear program, predicting President Barack Obama could face hurdles in Congress if negotiators reach a final deal.

McConnell spoke minutes after diplomats said on Sunday that negotiators at the Iran nuclear talks were expected to reach a provisional agreement to curb the country’s atomic program in return for tens of billions of dollars in sanctions relief. Secretary of State John Kerry has been leading the U.S. delegation in the talks in Vienna, which aims to impose long-term, verifiable limits on Tehran’s nuclear programs.

“This is going to be a very hard sell for the administration,” McConnell said on “Fox News Sunday” when asked about the likelihood of Congress signing off on a deal.

President Barack Obama has come under criticism from members of Congress and some U.S. allies in the Middle East who say the administration has conceded too much in the Iran talks. Iran has denied any nuclear weapon ambitions and said its program is meant to supply domestic energy and other peaceful purposes.

The current negotiations have run more than two weeks and blown through three deadlines. Because the talks are in overtime, Congress will have 60 days to assess the deal, requiring Obama to await that review before easing sanctions agreed to in a deal.

During those two months, lawmakers could try to build a veto-proof majority behind new legislation that could impose new sanctions on Iran or prevent Obama from suspending existing ones.

Sen. Bob Corker, the chairman of the Senate Foreign Relations Committee, said lawmakers would review any agreement carefully to ensure the Iranians are held accountable and that any violations can be enforced.

“At the end of the day I think people understand that if this is a bad deal that is going to allow Iran to get a nuclear weapon, they would own this deal if they voted for it, and so they’ll want to disapprove it,” said Corker, R-Tenn. “On the other hand, if we feel like we’re better off with it, people will look to approve it.”

New Jersey Sen. Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, said the pending deal made him anxious because the U.S. has gone from making sure Iran does not have nuclear capability to managing it.

Menendez said he would judge the agreement when he has all the elements but said Obama needs to make very clear to Iran that there’s a longer term deterrence, “because in 12 to 13 years we will be exactly back to where we are today except that Iran will have $100 (billion) to $150 billion more in its pocket and promoting terrorism throughout the Middle East.”

Obama downplayed chances for an Iran nuclear deal during a closed-door meeting with Senate Democrats last week, telling participants that an agreement was at best a 50-50 proposition.

McConnell said a resolution of disapproval is likely to be introduced in the Senate and predicted it would pass with more than 60 votes. If Obama vetoed the resolution, McConnell noted that the president would need 34 votes, or more than one-third of the Senate, to sustain it.

Menendez spoke on ABC’s “This Week.” Corker spoke on NBC’s “Meet the Press.”

(AP)