U.S. President Donald Trump said Monday he is holding off on a planned military strike against Iran scheduled for Tuesday because "serious negotiations" are underway, while warning the U.S. military remains ready to launch a large-scale assault if no acceptable deal is reached.

"I have been asked by the Emir of Qatar, Tamim bin Hamad Al Thani, the Crown Prince of Saudi Arabia, Mohammed bin Salman Al Saud, and the President of the United Arab Emirates, Mohamed bin Zayed Al Nahyan, to hold off on our planned military attack of the Islamic Republic of Iran, which was scheduled for tomorrow," Trump said on his social media platform Truth Social.

Trump said that, out of "respect" for the Gulf leaders, he had instructed Secretary of Defense Pete Hegseth, Chairman of the Joint Chiefs of Staff Gen. Daniel Caine, and US military commanders to stand down from the planned operation for now.

Trump's announcement in a social media post Monday came as he had threatened that the clock was ticking for Iran to strike a deal or fighting would renew after a fragile cease-fire.

The president did not offer details about the planned attack but said he instructed the U.S. military "to be prepared to go forward with a full, large scale assault of Iran, on a moment's notice, in the event that an acceptable Deal is not reached."

Trump has been threatening for weeks that the cease-fire struck in mid-April could end if Iran did not strike a deal, with shifting parameters for striking such an agreement.