McConnell spoke minutes after diplomats said today 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 US delegation in the talks in Vienna, which aim to impose long-term, verifiable limits on Tehran's nuclear programs.
Obama has come under criticism from members of Congress and some US allies in the Middle East who say the administration has conceded too much in the Iran talks. Iran has denied any nuclear weapons ambitions and said its program is intended for supplying 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.
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. On the other hand, if we feel like we're better off with it, people will look to approve it," said Corker.