The Hill has thoughts on the Iran deal. (EPA/MICHAEL REYNOLDS)

This article has been updated.

Congress greeted news of a framework agreement to curtail the Iranian nuclear program much as it has reacted to the months of negotiations that preceded it — with criticism from most Republicans, optimism from most Democrats, and a strong desire from both sides to play a direct role in the deal.

President Obama said Thursday that his administration would give Congress a thorough briefing on the details of the framework, but the outlines revealed so far did not immediately move any key lawmakers off of their previous positions — even as Obama warned against knee-jerk reactions.

"If Congress kills this deal not based on expert analysis, and without offering any reasonable alternative, then it's the United States that will be blamed for the failure of diplomacy," he said. "International unity will collapse, and the path to conflict will widen."

[Iran and world powers agree on parameters of Iranian nuclear deal]

Congressional sentiment was inflamed by Israeli Prime Minister Benjamin Netanyahu's early-March visit to Washington, where he told a joint meeting of Congress that any deal would "pave the way" to an Iranian nuke, and by the subsequent letter signed by 47 Republican senators sent to the Iranian regime, warning that Congress could reverse any deal made at the negotiating table.

Thursday's release of key details about the nuclear framework heralded a new phase of domestic politicking, where Obama will be seeking to keep Democrats unified behind him as he sells the deal to the public and on Capitol Hill, while Republicans determine how hard a line to draw against the terms negotiated over many months by the U.S. and five other foreign partners.

Key lawmakers struck a careful note Thursday, seeking above all to firm up Congress's role in reviewing the deal.

Sen. Bob Corker (R-Tenn.), chairman of the Senate Foreign Relations Committee, said lawmakers "must remain clear-eyed regarding Iran’s continued resistance to concessions, long history of covert nuclear weapons-related activities, support of terrorism, and its current role in destabilizing the region."

"If a final agreement is reached, the American people, through their elected representatives, must have the opportunity to weigh in to ensure the deal truly can eliminate the threat of Iran’s nuclear program and hold the regime accountable," said Corker, the lead sponsor of a bipartisan bill that would bring the nuclear deal to Congress for a 60-day review.

Congress is out of session until April 13, but the Senate Foreign Relations Committee is scheduled to mark up the review bill the day after members return. Corker said he is "confident of a strong vote" in its favor.

House Speaker John A. Boehner (R-Ohio), who invited Netanyahu to Washington and visited him in Israel earlier this week, also called for a legislative role in any deal: "Congress must be allowed to fully review the details of any agreement before any sanctions are lifted," he said in a statement. "After visiting with our partners on the ground in the Middle East this week, my concerns about Iran’s efforts to foment unrest, brutal violence and terror have only grown. It would be naïve to suggest the Iranian regime will not continue to use its nuclear program, and any economic relief, to further destabilize the region."

Rep. Peter Roskam (R-Ill.), a co-chairman of the House Republican Israel caucus, was more sharply critical of the advance toward a deal, saying in a statement that it "makes no demonstrable progress on the legitimate security concerns of the American people and the international community." Rep. Steve Israel, a House Democratic leader and frequent critic of the Iran talks, said he remains "highly skeptical" of a deal: "The details deserve and must get a vote by the U.S. Congress."

On the Senate side, the Republicans most critical of the deal showed no sign of softening their rebukes, and their Thursday statements indicated an emerging set of specific criticisms.

Sen. Tom Cotton (R-Ark.), the freshman who rocked Capitol Hill by putting together the letter addressed to Iranian leaders, said in an interview that the framework discussed Thursday represented "a list of concessions to put Iran on the path to a nuclear bomb."

“At this point, the only thing to do is walk away, impose new sanctions, and drive a tougher bargain,” he said.

Sen. Marco Rubio (R-Fla.), a Foreign Relations Committee member and a potential presidential candidate, said in a statement that the initial reports on the framework were "very troubling" and represented an "attempt to spin diplomatic failure as a success" while doing nothing about Iran's non-nuclear activities.

Both Cotton and Rubio said they were concerned that thousands of uranium-enrichment centrifuges would remain operational, even as negotiators said two-thirds or more would be decommissioned, and that the hardened Fordow enrichment facility would remain open, even if in a non-enriching capacity.

Senate Democrats, even those who had been skeptical of the negotiations, struck more positive notes Thursday, starting with Minority Leader Harry M. Reid (Nev.), who called on his colleagues to "take a deep breath, examine the details and give this critically important process time to play out."

"We must always remain vigilant about preventing Iran from getting a nuclear weapon but there is no question that a diplomatic solution is vastly preferable to the alternatives," he said.

Sen. Robert Menendez (D-N.J.), who until his Wednesday indictment on federal corruption charges served as the top Democrat on the Foreign Relations Committee, had been outspoken in his criticism of the Iranian regime and the dismal prospects for a diplomatic solution to its nuclear ambitions. But, like Corker, he did not characterize the deal in a Thursday statement but instead staked out the congressional interest in reviewing it.

"If diplomats can negotiate for two years on this issue, then certainly Congress is entitled to a review period of an agreement that will fundamentally alter our relationship with Iran and the sanctions imposed by Congress," he said. "The best outcome remains a good deal that ends Iran’s illicit nuclear weapons program. That requires a strong, united, and bipartisan approach from the administration and Congress."

Sen. Ben Cardin (D-Md.), the new ranking member, said in his own statement that "Congress has a role to play in this process," but he stopped short of endorsing a formal review period. "The best outcome is a strong diplomatic one," said Cardin, who is not a co-sponsor of the bipartisan review bill.

Obama on Thursday sought to forestall criticism of the deal by focusing attention on alternatives.

"When you hear the inevitable critics of the deal sound off, ask them a simple question: Do you really think that this verifiable deal, if fully implemented, backed by the world's major powers, is a worse option than the risk of another war in the Middle East?" Obama asked in the White House Rose Garden. "Is it worse than doing what we've done for almost two decades with Iran moving forward with its nuclear program and without robust inspections? I think the answer will be clear."

But the deal's fate may rest squarely on whether he can persuade congressional Democrats and a few centrist Republicans to leave him a free hand in the coming months to consummate the deal.

“I hope today’s announcement imbues Democrats with a sense of the seriousness of the stakes,” said Sen. Chris Murphy (D-Conn.), a junior member of the Foreign Relations Committee who has emerged as a strong administration ally.

Murphy said that it was critical that enough Democrats stand together to assure that the Corker bill mandating congressional review falls short of the two-thirds majority needed to override Obama’s veto.

Sen. Jeff Flake (R-Ariz.), another junior member of Foreign Relations, said the bloc of Republicans open to possible compromise is "bigger than it would seem to some people" and noted that "the country as a whole seems more open to a negotiated agreement than our conference has been."

A new Washington Post-ABC News poll found that Americans by a nearly 2-to-1 margin support the idea of striking a deal that would restrict the Iranian nuclear program in return for loosened sanctions.

[Poll: Clear majority supports nuclear deal with Iran]

“That said, it’ll be a tough sell, and it’s the final details that matter," Flake said, adding that he expects Secretary of State John Kerry, a former chairman of the Foreign Relations Committee, to personally make the case on Capitol Hill: "The administration is going to need all hands on deck.”

Despite the White House’s poor reputation for managing congressional relations, Murphy said that on this particular issue they have demonstrated success before and should be able to replicate that now. In 2014, as pressure built to ramp up sanctions on Iran, administration officials worked the Democrats to avoid a vote on the issue.

But multiple Republican senators said they expected to present a united front based on specific objections to the new framework, likely to be coordinated through Majority Leader Mitch McConnell (R-Ky.). who was overseas Thursday and did not issue a statement on the negotiations.

“Most of our guys have already staked out preventing Iran from nuclear capability as the bottom line," said Sen. John Thune (R-S.D.), chairman of the Senate Republican Conference. "Since this deal allows them to keep centrifuges and continue to enrich in some circumstances, those kind of particulars are going to be tough for most Republicans to handle or be for.”

McConnell was overseas Thursday, a spokesman said, and did not issue a statement on the negotiations.

“There may be some support," Thune added. "There are some Republicans who want to be supportive, want to be helpful and get to the right place. But there is such a difference of opinion about what that means.”