The Senate on Thursday rejected a bipartisan amendment to the Iran deal, and Republicans also rejected another amendment aimed at preventing the White House from negotiating a new agreement with Tehran.
The defeat marks the latest setback for negotiators, who were hoping to secure the final deal by the end of the year.
But the defeat was just the latest blow for the Obama administration, which had hoped to clinch the deal by Christmas.
Obama is seeking to convince Congress to allow him to use executive authority to bypass Congress to negotiate a new deal with Iran.
The president said Thursday that he wants to strike a deal by April 15.
The White House says it would be “irresponsible” for the Senate to allow the Senate vote to delay the deal.
The Senate passed a bipartisan bill in May that would have blocked the president from negotiating with Iran if Congress did not vote to approve a new U.S.-Iran deal by March 15.
Obama would have had to use Congress’ authority to waive the Iran sanctions in exchange for the agreement.
The new bill, Senate Bill 482, failed by a vote of 48-42, with Sen. Susan Collins of Maine joining Republicans in voting against it.
It also failed to pass the House.
The House has already passed the Senate version of the Iran agreement.
Republican leaders in the House have threatened to vote to kill the bill, which could also delay the vote on the new deal.
“Congressman Collins has not made a single public comment about this amendment,” White House press secretary Josh Earnest said Thursday.
“It’s a very partisan amendment, and I think it’s the wrong course for the president.”
The Iran deal is the most consequential U.N. Security Council resolution to date and is one of the most important legislative victories the Trump administration has achieved in his first two years in office.
Trump has pushed to negotiate the nuclear deal and his administration is still seeking to reach an agreement with Iran over its nuclear program, but it’s not clear whether it can do so without a major setback in the Senate.
A key element of the deal was the lifting of sanctions on Iran’s oil exports.
That move will be crucial to Trump’s goal of ending the country’s decades-long reliance on oil imports.