Opposition Republicans warned Iran’s leaders on Monday that any deal they might reach with President Barack Obama could be undone in 2017 when his term in office expires.

In an open letter signed by all but seven Senate Republicans, the lawmakers pointed out that without their consent a nuclear deal negotiated by the Obama Administration would be nothing more than an “executive agreement” that could easily be undone by the next president.

None of Obama’s fellow Democrats signed the letter which they described as a “stunt” and an attempt on Republicans’ part to “sabotage” the negotiations with Iran.

Administration officials similarly derided the letter — which was first reported by Bloomberg — as a partisan effort to undermine the president’s foreign policy.

Obama himself accused the Republicans of siding with hardliners in Tehran who also oppose an agreement that would limit Iran’s nuclear program. “It’s an unusual coalition,” he told reporters.

Republicans have long criticized Obama’s outreach to a regime that sponsors terror against America and its allies in the Middle East, including Israel. The letter was apparently prompted by reports last week that the deal under negotiation would “sunset” ten years after being ratified, theoretically allowing Iran to build a nuclear weapon in a decade.

Conservatives see this as a fatal flaw in the agreement. Israeli prime minister Benjamin Netanyahu told Congress last week Obama was about to make a “bad deal” and urged lawmakers to stop him.

Republicans had invited the Israeli leader to speak without consulting Democrats or the White House.

Neither Netanyahu nor Republicans have spelled out under what conditions they could live with a nuclear-capable Iran. The Islamic republic itself is adamant about its “right” to enrich uranium for peaceful purposes and denies it seeks atomic weapons.

The United States and other world powers are negotiating with Iran to reach a framework agreement later this month and a final deal in June. Iran seeks relief from sanctions on its oil-based economy while the West wants assurances it won’t build nuclear bombs.