House Speaker John Boehner vowed "to do everything possible" to stop the Iran nuclear deal from being enacted.

In remarks to reporters following a closed-door meeting with House Republicans, Boehner said the deal "faces serious skepticism" in the United States, even though the United Nations endorsed the agreement on Monday.

The Obama administration is ramping up efforts to sell the deal to Congress. Secretary of State John Kerry and other Cabinet members will come to Capitol Hill Wednesday and Thursday to brief lawmakers.

"Let me just assure you that members of Congress will ask much tougher questions this afternoon when we meet with the president's team," Boehner said, taking a swipe at the U.N.'s decision to approve the deal. "Because a bad deal threatens the security of the American people, and we're going to do everything possible to stop it."

Ron Dermer, the Israeli ambassador to the United States, warned a group of about 40 conservatives against the deal when he met with them Wednesday morning at the Capitol Hill Club.