By Patricia Zengerle and Idrees Ali
WASHINGTON (Reuters) - The Obama administration on Wednesday kicked off its push for approval of the Iran nuclear deal by dispatching Vice President Joe Biden to Congress, where he assured Democrats nothing in the pact would preclude military action if Tehran violated the agreement.
"He stated clearly that nothing in the agreement takes the military option off the table," U.S. Representative Steve Israel said after leaving the closed-door meeting between Biden and House of Representatives Democrats.
The meeting took place a few hours before President Barack Obama held a news conference making his case for the deal.
The White House needs support from Obama's fellow Democrats in the Senate and the House to preserve the agreement between the United States and five other world powers, given intense Republican opposition to the pact.
But enough Democrats are expected to stand behind the deal that it will survive the congressional review.
Democrats leaving the meeting said Biden told them rejecting the pact would wreck the international sanctions regime against Iran.
"He made the important point that he could guarantee that if the U.S. walked away the entire sanctions regime would crumble," Representative Jan Schakowsky said.
They also said he had focused on technical aspects, taking 45 minutes of questions.
Afterwards, some Democrats said they expected to support the deal.
"I am proud of the president on this issue ... I lean to a 'yes' right now," Representative Bill Pascrell said.
Biden said he was confident Democrats would back it once they knew what was in it. "I think we'll be all right," he told reporters.
Under legislation passed overwhelmingly by Congress and signed into law by Obama in May, the House and Senate have 60 days to vote to approve it, or back a resolution of disapproval or do nothing and allow the deal to take effect.
The 60-day window is expected to open this week, when Congress receives the agreement and supporting documentation.
If a disapproval resolution passes, it would cripple the agreement by barring Obama from waiving most U.S. sanctions.
But Obama has promised to veto such a resolution if it reaches his desk.
To override a veto, opponents would need two-thirds majorities in both the House and Senate, meaning the deal would be preserved if it is supported by just 34 of the 100 senators.
There are 46 members of the Senate Democratic caucus, including 44 Democrats and two independents.
(Additional reporting by Susan Cornwell, Richard Cowan, Doina Chiacu and Alex Wilts; Editing by James Dalgleish)