President Donald Trump speaks during an executive order signing ceremony in the Oval Office of the White House in Washington, DC, Aug. 3. EPA-Yonhap

WASHINGTON/DUBAI — U.S. President Donald Trump said on Monday that talks with Iran were under way, warning that it was a "last chance" for Tehran to sign a good deal to end the five-month-old war, but Iran denied that any negotiations were being held or planned.

The contradictory statements suggest there is little prospect for a diplomatic resolution to the war anytime soon.

"They are going on right now," Trump told reporters at an Oval Office event when asked about the state of negotiations, saying the sides were talking at the request of Iran, Saudi Arabia, the United Arab Emirates and Qatar, among others.

"This is a last chance for them (Iran) to sign a good document," he said.