President Donald Trump said that the United States would not leave Iraq until the country paid the United States for the military base built there.

“We have a very extraordinarily expensive airbase that’s there. It cost billions of dollars to build. Long before my time,” he said. “We’re not leaving unless they pay us back for it.”

Trump commented on Iraq and Iran as he traveled back to Washington, DC, from Mar-a-Lago after both countries protested his decision to eliminate Iranian General Qasem Soleimani in Bagdhad in a drone strike on Friday.

In response to the strike, the Iraqi parliament on Sunday passed a resolution calling on the government to expel American troops from Iraq.

The president repeated that invading Iraq was “the worst decision ever made in the history of our country” and that he would continue to withdraw troops from the country.

“Iraq, by the way, they didn’t knock down the World Trade Center,” he said. “That’s been very nicely proven.”

But Trump said that the United States had spent billions of dollars in Iraq, and he threatened sanctions on the country if they tried to force out the United States.

“If they do ask us to leave, if we don’t do it in a very friendly basis, we will charge them sanctions like they’ve never seen before ever,” he said. “It’ll make Iranian sanctions look somewhat tame.”

President Trump visited the Al Asad Air Base in Iraq in December 2018, personally viewing the military base constructed in the country.