Some of President Barack Obama’s fellow Democrats expressed skepticism and Republicans voiced outright hostility Tuesday to the landmark Iranian nuclear deal.

Under the historic accord, Iran’s nuclear program would be curtailed in exchange for billions of dollars in relief from international sanctions. The agreement aims to avert the threat of a nuclear-armed Iran and another U.S. military intervention in the Middle East.

“I was skeptical at the beginning of this process, and I remain skeptical of the Iranians,” said Rep. Steve Israel, the highest ranking Jewish Democrat in the House. “In the fall, there will be a vote on this deal, and my obligation is to review every word, sentence and paragraph of the deal to ensure it satisfies my continued concerns.”

“If it’s as bad a deal as I think it is,” said Republican House Speaker John Boehner of Ohio, “we’re going to do everything we can to stop it.”

Sen. Bob Menendez, formerly a ranking member of the Foreign Relations Committee, said he was concerned that the deal “ultimately legitimizes Iran as a threshold nuclear state.”

“I’m concerned the red lines we drew have turned into green lights: that Iran will be required only to limit rather than eliminate its nuclear program, while the international community will be required to lift the sanctions,” said Menendez, D-New Jersey.

After receiving a copy of the agreement, lawmakers will have 60 days to read the fine print, vote yea or nay — or take no action.

If Congress votes to disapprove it, Obama reiterated Tuesday that he would veto it. A two-thirds majority in both the House and Senate would be needed to override a veto.

Many Republicans, as expected, are vehemently opposed to the agreement. That’s not surprising since the GOP-led House invited Israeli Prime Minister Benjamin Netanyahu to speak before a joint meeting of Congress earlier this year. Netanyahu assailed the negotiations with Iran, which has threatened to destroy Israel.

“It’s like giving an alligator more teeth and thinking now they may be nice to you,” said Rep. Ted Yoho, R-Florida.

Senate Majority Leader Mitch McConnell of Kentucky said the agreement was flawed. “Given what we do know so far it appears that Republicans and Democrats were right to be deeply worried about the direction of these talks,” he said on the Senate floor.

Even if Congress votes to disapprove the deal, it doesn’t scuttle the agreement.

The only way Congress can thwart the Iran deal is by passing new sanctions legislation or stripping away the authority Obama currently has to waive those sanctions that were imposed earlier by Congress. Moreover, even if Congress rejects the deal with Tehran, Obama could use his executive pen to offer a hefty portion of sanctions relief on his own. He could take unilateral actions that — when coupled with European and U.N. sanctions relief — would allow him to implement the deal. Obama can’t lift the congressionally mandated sanctions; only Congress can do that.

“If this agreement is what the administration says it is, it is a major, historic diplomatic breakthrough,” said Sen. Barbara Boxer, D-California.

The foreign relations committees in both chambers — and possibly other panels on intelligence and the armed services — are expected to quickly schedule hearings. It appears unlikely, though, that Congress will take any formal action before the August recess, when they most certainly will hear from constituents on the issue.

When it comes to a vote, all eyes will be on Democrats to figure out whether they will back the deal brokered by the administration or turn their back on the president, as many of his fellow Democrats did in a recent battle involving trade negotiating authority for presidents.

Key senators to watch: New York Sen. Chuck Schumer, the No. 3 Democrat in the chamber; Menendez, who has bucked the White House by voicing skepticism that Iran can be trusted to abide by terms of any deal; and Maryland Sen. Ben Cardin, the ranking Democrat on the Senate Foreign Relations Committee.

“Supporting or opposing this agreement is not a decision to be made lightly, and I plan to carefully study the agreement before making an informed decision,” Schumer said.

Cardin urged his colleagues to conduct a thorough, rigorous and even-handed review of the deal.

“There is no trust when it comes to Iran,” Cardin said. “In our deliberations we need to ensure the negotiations resulted in a comprehensive, long-lasting, and verifiable outcome that also provides for snap-back of sanctions should Iran deviate from its commitments.”

(AP)