U.S. President Donald Trump announced on social media Monday that Israel and Iran had reached a “complete and total ceasefire,” set to be phased in over the next 24 hours.

The unexpected declaration came amid escalating tensions between the two Middle Eastern powers, but key players quickly cast doubt on the claim.

The ceasefire is set to start in approximately six hours, the president said.

“It has been fully agreed by and between Israel and Iran that there will be a Complete and Total CEASEFIRE (in approximately 6 hours from now, when Israel and Iran have wound down and completed their in progress, final missions!), for 12 hours, at which point the War will be considered, ENDED,” the president wrote on social media.

Reuters report said Trump appeared to suggest that Israel and Iran would have some time to complete any missions that are underway, at which point the ceasefire would begin in a staged process.

Earlier, Iran said it launched an attack on U.S. forces at Al Udeid Air Base. Qatar stated that its air defences successfully thwarted the strike on the facility—which had been evacuated—shooting down 18 of the 19 missiles fired.

The BBC noted that it had not received independent confirmation of a ceasefire from Iranian sources.

It comes after Iran says more than 400 people, including 13 children, have been killed and at least 3,056 others wounded since Israel launched its attack on June 13. In Israel, at least 24 people have been killed in Iranian strikes