Washington: The Republican-led House has approved a bill that would undercut the milestone nuclear deal with Iran, a largely symbolic move that highlights strident GOP opposition to the international accord.

On a largely party-line vote, the House backed the measure 249-176. It calls for prohibiting the Obama administration from buying more of Iran’s heavy water, a key component in certain nuclear reactors. The White House has said removing the country’s surplus heavy water denies Tehran access to a material that may be stored for potential nuclear weapons production.

The US, other world powers and Iran finalised the nuclear pact on July 14, 2015, after nearly two years of intense negotiations. In exchange for Tehran rolling back its nuclear programme, the US and other world powers agreed to suspend wide-ranging oil, trade and financial sanctions that had choked the Iranian economy.

President Barack Obama would veto the House bill if it reaches his desk, according to the White House. But Republicans said Iran should be punished for continuing to manufacture heavy water, not rewarded with millions of US taxpayer dollars that may end up being used to support terrorism or Tehran’s ballistic missile programme.

“Why are we giving the seal of approval to Iran’s heavy water production?” asked Representative Ed Royce, the Republican from California and the chairman of the House Foreign Affairs Committee.

The heavy water measure is the first of three bills targeting the seven-nation nuclear pact that are expected to clear the chamber before Congress departs Washington for a lengthy summer recess.

The bills have antagonised Democrats, who have accused the GOP of jettisoning bipartisanship in favour of election-year politics. They said both parties have worked in the past to address Iran in a way that demonstrated unity instead of dissension.

Representative Eliot Engel, the Democrat from New York, who opposed the nuclear deal, said he agreed that the US shouldn’t be buying Iran’s heavy water. But Republican leaders wanted “political theatre,” he said, and they hustled Kansas Representative Mike Pompeo’s bill to the House floor and barred any amendments to the legislation.

“That’s why this bill is so deeply flawed,” Engel, the House Foreign Affairs Committee’s senior Democrat, said. “That’s why it has no chance of becoming law.”

A measure similar to the House bill died in the Senate two months ago.

Heavy water, formed with a hydrogen isotope, is not radioactive but has research and medical applications and can also be used to produce weapons-grade plutonium. Under the nuclear deal, Iran is allowed to use heavy water in its modified Arak nuclear reactor, but must sell any excess supply of both heavy water and enriched uranium on the international market.

The Obama administration announced in April plans for the Energy Department to purchase 32 metric tons of heavy water for $8.6 million (Dh31.6 million) from a subsidiary of the Atomic Energy Organisation of Iran. The heavy water is expected to arrive in the US in the coming weeks and will be stored at the Oak Ridge National Laboratory in Tennessee and then resold on the commercial market for research purposes.

The nuclear agreement has emerged as an issue in a few Senate races. In Arizona, the campaign of Senator John McCain, a Republican seeking his sixth term, issued a news release on Wednesday linking the “reckless” nuclear deal to his Democratic opponent, Representative Ann Kirkpatrick.