By Patricia Zengerle and David Lawder
WASHINGTON (Reuters) - A rebellion by conservative Republicans in the House of Representatives on Wednesday delayed Congress' first vote on the Iran nuclear agreement and raised the possibility that lawmakers might never vote on a resolution disapproving of the pact.
The House was supposed to vote on a procedural motion to begin debate on Wednesday, but it was put off after some Republicans said they wanted to push President Barack Obama to provide more information about the deal.
Instead, House Republican leaders scheduled a late afternoon meeting to discuss how to proceed.
Under a law Obama signed in May, Congress has until Sept. 17 to vote on the nuclear agreement between the United States, five other world powers and Tehran.
A resolution of disapproval, if passed, would sink the deal, under which Iran gains relief from sanctions in return for curbing its nuclear program, by eliminating Obama's ability to waive many U.S. sanctions on Iran.
Obama has secured enough votes from his fellow Democrats to sustain a veto of the measure, even if the Republican-led Congress approves it.
The rebel Republicans, led by Representative Peter Roskam, said the Obama administration had not provided all the required information about the deal. They said it includes "secret side deals" about nuclear inspections that have not been fully revealed.
The White House dismissed that suggestion. "If Congress does not vote, this agreement goes into effect. It's as simple as that," spokesman Eric Schultz said.
Senate Republicans also expressed doubts. "As I understand the law... we have to act before Sept. 17, which is next week, or the deal goes forward," Senate Majority Leader Mitch McConnell told reporters.
The dispute in the House arose after announcements on Tuesday that deal supporters had mustered 42 votes in the Senate, more than enough to block a disapproval resolution before it could be passed, if all of the votes hold.
Even if senators are unable to use the Senate's filibuster procedural rule to block the measure, they have far more than the 34 votes in the 100-member Senate needed to sustain Obama's promised veto.
To override a veto, deal opponents would need two-thirds majorities in both the Senate and the House.
U.S. Secretary of State John Kerry and Energy Secretary Ernest Moniz met with pro-deal senators on Wednesday to bolster support.
Kerry urged lawmakers to vote as quickly as possible. Deal supporters hope at least 41 senators will vote to block the measure, but Senator Richard Durbin, the chamber's top Democratic vote counter, said he did not yet have a final number.
(Additional reporting by Julia Edwards on Air Force One and Richard Cowan in Washington; Editing by David Storey and Steve Orofsky)