The framework nuclear agreement announced Thursday between world powers and Iran sets the stage for Congress and foreign nations to try to change — or kill — a final deal.

The United States, United Kingdom, France, Russia, China and Germany reached an understanding with Iran on limits to Iran’s nuclear program in return for lifting crippling economic sanctions.

Negotiators now have until June 30 to fill in the critical details to assure Iran it will get relief from the sanctions as soon as possible, and guarantee the world powers that Iran won’t develop a nuclear weapon. Lying in wait are Congress, Iran’s enemies in the Middle East and difficult issues that may reshape, delay or doom a final accord.

U.S. Congress

President Obama wants a final agreement that is short of a formal treaty to skirt approval by a skeptical Congress, which might make changes unacceptable to Iran. Not so fast, lawmakers say. The Senate Foreign Relations Committee will take up legislation that requires congressional approval of a nuclear deal, committee Chairman Bob Corker, R-Tenn., said.

“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,” Corker said.

Sen. Chuck Schumer, D-N.Y., who has co-sponsored the bill and had expressed skepticism as the deal was emerging, said he’ll “be giving the framework a very careful look.”

Schumer’s emergence as the next Senate Democratic leader could give critics — now mostly Republicans — more clout, said Mark Dubowitz, executive director of the Foundation for Defense of Democracies, who has testified before Congress on Iran sanctions.

Schumer is being lobbied heavily by both his pro-Israel constituents and the White House, Dubowitz said. “He’ll be the bellwether for which way wavering Democrats go on this.”

A second Senate bill would increase sanctions on Iran after June 30 if there is no comprehensive agreement by then. Obama has said he would veto both bills because they would derail the talks.

The wrangling begins April 14, when Corker’s committee will debate whether the results of the past week’s talks were satisfactory, and discuss how to proceed. One option that Obama fears could kill the deal: new sanctions to squeeze additional concessions from Iran. Instead, Obama has warned, Iran may walk away from the talks and accelerate its nuclear program.

Israel

Israeli Prime Minister Benjamin Netanyahu, a vehement opponent of any deal that leaves Iran’s nuclear program intact, has already launched a fresh round of sharp attacks. He’s trying to rally Congress, other world powers and Iran’s rivals in the Middle East — such as Saudi Arabia — to demand a stronger deal that ensures Iran won’t develop a nuclear bomb in secret.

Any move to eventually lift sanctions against Iran as part of the deal would boost Iran’s economy and give it “tremendous means to propel its aggression and terrorism throughout the Middle East,” Netanyahu said Friday. He added that allowing Iran to keep its nuclear program could “spark a nuclear arms race (in the region) … and it would greatly increase the risks of terrible war.”

He said a better deal would link lifting sanctions beyond its nuclear program to ending Iran’s support of terrorists around the world and its threats to annihilate Israel.

Israel could disrupt the negotiations by assassinating Iran’s nuclear scientists and sabotaging or attacking its nuclear facilities, which Iran has accused Israel of doing in the past. That could scuttle a final deal, said George Perkovich, an expert on nuclear proliferation at the Carnegie Endowment for International Peace.

Details

The framework agreement left key details to be ironed out, including the pace of sanctions relief, when and to what extent Iran will explain evidence of a past nuclear weapons program — which it denies ever having — and when it will take the steps spelled out in the deal.

The Obama administration and Iran showed they interpret the deal differently just within a few hours of its announcement.

Secretary of State John Kerry said that “in return for Iran’s future cooperation,” relief from U.S. and international sanctions will be provided “in phases.” Iran could begin qualifying for such relief as soon as four months to a year after any agreement begins, Kerry said.

Iran’s Foreign Minister Javad Zarif, however, tweeted a response that denied sanctions relief would be gradual. “Iran/5+1 Statement: “US will cease the application of ALL nuclear-related secondary economic and financial sanctions.” Is this gradual?”

Deadline

The talks have proceeded under a six-month agreement signed in November 2013 that has been extended several times already and is now due to expire in three months. Just as Tuesday’s self-imposed deadline was missed by two days, the June 30 deadline could be postponed, too.

From the U.S. standpoint, keeping the 2013 interim agreement now in force is an advantage, because it stops Iran from advancing its nuclear program and building its stockpiles of nuclear fuel, while depriving Iran of significant economic relief, said Gary Samore, a former arms control coordinator for Obama.

“There are many problems that could easily make it difficult to get an agreement by June 30,” Samore said. “At that point I would expect another extension.”

Dubowitz agrees. “There is no such thing as a deadline in these negotiations,” he said. “The only deadline I think the president is concerned about is January 2017, when his second term as president expires.”