Lawmakers returning to Washington from their summer recess are plunging immediately into bitter, partisan debate over the Iran nuclear accord.

The deal struck by Iran, the U.S. and five world powers in July is aimed at curbing Iran’s nuclear program in exchange for hundreds of billions of dollars in relief from economic sanctions.

Republicans who control the House and Senate strongly oppose the pact, saying it makes dangerous concessions to Iran. They hope to push through a resolution of disapproval this week.

If they succeed, President Barack Obama would veto the resolution, and Democrats have already lined up enough votes to uphold his veto.

The question as Congress reconvenes Tuesday from a five-week break is whether the disapproval resolution will get through the Senate — or whether Democrats will have the votes to block it with a filibuster.

That’s not yet certain. Democrats are three votes shy of the 41 they would need to mount a filibuster. Five senators have yet to announce their position, including several who might end up opposing the Iran deal.

The Obama administration picked up support for the deal over the Labor Day weekend from former Secretary of State Colin Powell and Rep. Debbie Wasserman Schultz, the head of the Democratic National Committee and an influential Jewish lawmaker.

Leaders of Israel have been strongly lobbying against the deal they say could empower Iran, but have succeeded in winning over only three Senate Democrats, albeit all of them prominent figures — Chuck Schumer of New York, Robert Menendez of New Jersey and Ben Cardin of Maryland, the top Democrat on the Senate Foreign Relations Committee.

But the majority of Democrats have swung behind the president, including Senate Minority Leader Harry Reid, D-Nev., who has scheduled a speech on the topic for Tuesday morning at the Carnegie Endowment for International Peace.

Republicans unanimously oppose the agreement, but predictions that it would dominate discussion during Congress’ August recess never came to pass as political headlines were largely overtaken by Donald Trump’s presidential candidacy. The two topics will converge on Wednesday, though, when Trump joins Texas Sen. Ted Cruz for a rally to oppose the deal — the same day Hillary Rodham Clinton delivers a speech supporting it.

The deal sets Iran back so that it is at least a year away from being able to produce enough nuclear material for a weapon, before the restrictions ease after a decade. Iran is currently assessed to be only 2 to 3 months away from being able to enrich enough uranium for a bomb, if it decides to do so.

(AP)