Trump expects to sign a deal with Iran on Sunday, but Tehran may want to avoid giving him a gift on his birthday

"Seems fitting that this should serve as the endgame."

A memorandum of understanding that ends the Iran war and reopens the Strait of Hormuz could be imminent, after weeks of dashed hopes and on-again, off-again talks.

But the timing of an MOU could emerge as a last-minute snag.

President Donald Trump insisted on Saturday that he will sign a deal on Sunday, which also happens to be his 80th birthday.

That came after Pakistan’s prime minister said earlier on Saturday that an agreement is closer than “ever before” and expected it to be finalized within 24 hours.

Pakistan, which has served as a mediator between the U.S. and Iran, is preparing for an electronic signing, followed immediately by technical-level talks next week.

But Tehran pushed back, with its Fars News Agency denying that anything will be signed on Sunday and instead dismissing “Trump’s strange insistence” for that day.

“An hour ago, Trump once again emphasized that the memorandum of understanding with Iran will be signed on Sunday,” it said in a post on X. “This comes even as Iranian officials have explicitly stated that the agreement has not been finalized and will definitely not take place on Sunday.”

Iran’s foreign ministry also maintained that the MOU will not be signed on Sunday—but didn’t rule out that it could happen in the coming days.

To be sure, there have been several times when it looked like both sides were on the verge of a deal, but nothing happened. Reading between the lines this time, however, Iran watchers see a less substantive issue at play.

“They don’t want to give Trump a birthday gift! (seriously, this is being discussed as an important factor among Iranian commentators),” said Hamidreza Azizi, an analyst at SWP Berlin.

Eurasia Group analyst Gregory Brew agreed, and also quipped, “Seems fitting that this should serve as the endgame.”

He predicted the MOU could be signed when it’s Sunday night in the eastern U.S., but early Monday morning in Iran.

Of course, more serious matters could still derail the MOU. For example, Iran has vowed to charge fees on ships crossing the Strait of Hormuz, a non-starter for the U.S.

Tehran is also demanding immediate sanctions relief and the unfreezing of assets, while the U.S. has said that could come in phases as Iran satisfies its end of the bargain, especially on winding down its nuclear program.

The U.S. and Iran are also still exchanging fire, with Central Command saying Friday that U.S. forces shot down Iranian drones that were targeting commercial ships transiting the Strait of Hormuz.

Meanwhile, Trump is planning other birthday activities. On Sunday, UFC will stage a fight on the South Lawn of the White House, the first such event at the executive mansion.

The mixed martial spectacle, which features a giant claw-like structure that was built around UFC’s Octagon, is timed for Trump’s birthday and the celebration of the nation’s 250th anniversary.

Last year, Trump celebrated his 79th birthday with a military parade along the streets of Washington, DC, that coincided with the Army’s 250th birthday.

This story was originally featured on Fortune.com