The U.S. Congress will have a say on a nuclear deal with Iran, under a new agreement reached with the White House, BBC News reports.

President Barack Obama withdrew his opposition to a bipartisan bill that was unanimously passed through the Senate Foreign Relations Committee.

He has agreed to sign the bill, which gives Congress the right to reject any forthcoming agreement with Iran.

An outline agreement on the future shape of Iran's nuclear program was reached after marathon talks in April.

The U.S., Iran, and four other nations have set a deadline of June 30 to finalize a deal which would ease western sanctions in exchange for restrictions on Iran's nuclear program.

Some Republicans have argued against the deal, saying Iran has received too many concessions. They have always insisted they must have a say if any agreement means economic sanctions levied by Congress against Iran will be lifted.

The bill is now likely to clear both houses in the Republican-controlled Congress.

An earlier version of the bill had placed a 60-day halt to any plan by Obama to lift sanctions on Iran. But that review period has been reduced to 30 days.

Obama will still be able to lift sanctions he himself imposed through executive action but he would be unable to ease those imposed by Congress.