During his speech announcing the nuclear deal with Iran, President Obama said he welcomed robust discussion of the agreement but would ultimately veto legislation that "prevents the successful implementation of this deal." (AP)

In an indication of the battle to come over the just-completed Iran nuclear deal, senior lawmakers of both parties have called on President Obama to stop a vote in the U.N. Security Council, scheduled for next week, to officially endorse the agreement and set terms for its implementation.

In a letter Thursday, Sen. Bob Corker (R-Tenn.), chairman of the Foreign Relations Committee, and ranking Democrat Sen. Benjamin L. Cardin (Md.) urged Obama to postpone U.N. consideration of the agreement until Congress can review it and potentially vote on its own assessment.

The Republican chairmen of the House Homeland Security and Foreign Affairs committees sent a similar letter to the White House on Wednesday.

Corker, speaking as he left a meeting with Vice President Biden on Iran, called the U.N. plans “an affront to the American people.”

Administration officials dismissed concerns that the U.N. would take precedence over Congress, saying the resolution does not begin to implement the deal for 90 days, a delay they said was expressly included to ensure lawmakers would have enough time to weigh in first. The deal requires Iran to sharply curtail its nuclear activities, under international verification, in exchange for lifting economic sanctions.

What's next for Iran after the nuclear deal

In a compromise reached in May with Congress, Obama agreed not to use his authority to waive U.S. sanctions against Iran for at least 60 days after a deal was reached. The review begins when the text of the agreement is delivered to lawmakers this weekend.

During that period, Congress has the option of voting, by a simple majority, to “disapprove” it and permanently bar a sanctions waiver. Obama has said he would veto such legislation. For the moment, the administration is certain it has enough votes among Democrats to prevent a veto override, which requires a two-thirds vote in both chambers.

If a veto were overridden — cementing Congress’s official disapproval — a State Department official said this week that “we don’t have authority to provide U.S. sanctions relief” and that “the deal won’t proceed.”

White House deputy press secretary Eric Schultz said Thursday that “we will not begin implementation of the plan until after the congressional review period is over.” The 90-day delay, officials said, also gives Iran time to begin taking steps to comply with the deal and allows the International Atomic Energy Agency to prepare for its inspection and verification role.

The U.S.-authored resolution was circulated to Security Council members Wednesday, in accordance with language in the deal requiring it to be submitted “promptly” and voted on “without delay.” Approval is assured, since all five permanent Security Council members, with veto authority, negotiated the deal and signed off on it upon completion in Vienna early Tuesday.

“It would have been a little difficult, when all the members . . . wanted to go to the United Nations and get an endorsement of this . . . for us to say, ‘Well excuse me, the world, you should wait for the United States Congress,’ ” Undersecretary of State Wendy Sherman, the lead U.S. negotiator, said Thursday.

“So what we worked out is a process that allows this time and space for the congressional review before it takes effect, and there may be other legislatures who also want to look at this,” Sherman said. U.S. negotiating partners in the Iran talks included Britain, France, Russia, China, Germany and the European Union.

Iran has finally reached a nuclear deal with the U.S. and international partners. Here's what's in the deal, and what happens next. (Gillian Brockell and Julio C. Negron/The Washington Post)