“I don’t think any of [us] feel pressure, either by Chuck Schumer’s rejection of this deal or the president’s full-throated support of this deal,” the Missouri Democrat told NBC’s “Meet the Press.”

Congressional GOP leaders said they will hold votes in the House and the Senate next month on resolutions to disapprove of the deal, setting up a dramatic showdown as the White House tries to corral support.

Under the Iran Nuclear Agreement Review Act passed earlier this year, Congress has a certain amount of time to consider the agreement Mr. Obama and other world leaders struck with Iran. If Congress disapproves, the president has a chance to veto it and then try to survive an override attempt on Capitol Hill.

That means opponents of the deal have to muster a two-thirds majority.