“It has been fully agreed by and between Israel and Iran that there will be a Complete and Total CEASEFIRE,” Trump posted on social media, although there was no immediate word from either country on the announcement.

The ceasefire would start with Iran and then joined by Israel 12 hours later, with Trump saying the respective sides would “remain PEACEFUL and RESPECTFUL.” The phased-in ceasefire means the war could end as soon as Wednesday.

“This is a War that could have gone on for years, and destroyed the entire Middle East, but it didn’t, and never will!” Trump said.

The announcement came after Iran attempted to retaliate for the U.S. assault with a Monday missile strike aimed at a major U.S. military installation in the Gulf nation of Qatar. Trump separately thanked Iran on social media for giving the U.S. and allies “early notice” of the retaliation.

The president expressed hope that Tehran — with its reprisal for the U.S. bombardment of three key Iranian nuclear facilities — had “gotten it all out of their ‘system’” and that the moment would lead to a de-escalation in the Israel-Iran war, an event that occurred a few hours after the posting.

“I am pleased to report that NO Americans were harmed, and hardly any damage was done,” Trump said on social media. “I want to thank Iran for giving us early notice, which made it possible for no lives to be lost, and nobody to be injured. Perhaps Iran can now proceed to Peace and Harmony in the Region, and I will enthusiastically encourage Israel to do the same.”

The Iranian attack on U.S. forces at Qatar’s Al Udeid Air Base marked Tehran’s first act of direct retaliation against the U.S. since Trump ordered strikes on Iran’s nuclear facilities.

Leon Panetta, who served as CIA director and defense secretary under former President Barack Obama, said Iran’s restrained response suggests that “their ability to respond has probably been damaged pretty badly.” He also said it’s a potential signal “they’re not interested in escalating the war, either with Israel or the United States.”

Trump said Iran launched 14 missiles at the base, a sprawling facility that hosts the forward headquarters of the U.S. military’s Central Command and was a major staging ground during the U.S. wars in Iraq and Afghanistan. The base houses some 8,000 U.S. troops, down from about 10,000 at the height of those wars.

The president said 13 of the Iranian missiles “were knocked down,” by U.S. air defense systems while one was “’set free’ because it was headed in a nonthreatening direction.”

Hours before Iran launched its attack on Monday, the U.S. Embassy in Qatar issued an alert on its website urging American citizens in the energy-rich nation to “shelter in place until further notice.” The Qatari government issued an extraordinary order to shut its busy airspace.

The attack came as global markets were trying to ascertain what lays ahead after the U.S. struck key Iranian nuclear facilities over the weekend with a barrage of 30,000-pound bunker busting bombs and Tomahawk missiles.

Iran’s parliament has approved cutting off the Strait of Hormuz, a narrow shipping lane in the Persian Gulf that about 20% of global oil and gas passes through. It’s now up to Iran’s national security council to decide whether to move forward with the idea, which could lead to a spike in the cost of goods and services worldwide.

So, far the markets appear to be a responding with a relative measure of calm. By Monday afternoon, oil prices were nearly back to where they were before the fighting began over a week ago.

Trump earlier Monday called on the U.S. and allied oil producing nations to pump more oil and “KEEP OIL PRICES DOWN.”

Many energy industry analysts had been skeptical that Iran would go forward with a full closure of the strait, something that it has threatened to do in the past.

Iran would have faced the possibility of retaliation against its own shipments and the possibility that the move would upset China, the biggest purchaser of Iranian crude.

The U.S. and allies pressed Russia in the leadup to Moscow’s 2022 invasion of Ukraine with threats to its oil industry, and then followed through as many Western oil companies pulled out of the country and the U.S. and Europe imposed sanctions on Russian industry.

But Iran is far less integrated into the global economy than Russia, which was reliant on European markets for its oil and gas exports and still went forward with the invasion despite U.S. warnings.

Colby Connelly, a senior fellow at the Middle East Institute, cautioned that “if the 2020s have taught us anything so far, it’s that economic ties don’t always prevent conflict.”

As for Iran’s future, White House press secretary Karoline Leavitt on Monday appeared to play down Trump calling into question the future of Iran’s ruling theocracy, seemingly contradicting his administration’s earlier calls on Tehran to resume negotiations and avoid an escalation in fighting.

“It’s not politically correct to use the term, ‘Regime Change,’ but if the current Iranian Regime is unable to MAKE IRAN GREAT AGAIN, why wouldn’t there be a Regime change???” Trump posted on social media. “MIGA!!!”

Leavitt said Trump’s “posture and our military posture has not changed.”

“The president was just simply raising a question that I think many people around the world are asking,” Leavitt said.