They predicted 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.
