If the Iraqi government forces the removal of U.S. forces, Baghdad will face “sanctions like they’ve never seen before,” President Donald Trump said Sunday.

Trump said the prospective economic penalties would far outweigh the crippling sanctions the U.S. has imposed on Iran, adding: “If there’s any hostility, that they do anything we think is inappropriate, we are going to put sanctions on Iraq, very big sanctions on Iraq.”

The warning comes after Iraq’s parliament passed a resolution calling on the government to oust U.S. troops in retaliation for the assassination of Iranian general Qassem Soleimani, the former chief architect of Tehran’s regional operations.

The State Department expressed its disappointment over the vote, urging Baghdad to reconsider it.

Trump framed his threat of biting sanctions in terms of U.S. military investments in Iraq, referencing in particular an air base the U.S. has helped develop.

“We have a very extraordinarily expensive air base that’s there. It cost billions of dollars to build,” he added. “We’re not leaving unless they pay us back for it.”

The president did not specify which air base he was referring to, but it was likely the Al Asad airbase in central Iraq’s Anbar province. The facility is jointly operated by U.S. and Iraqi forces.

Soleimani, the head of Iran's Revolutionary Guards' elite Quds force, was killed in a U.S. drone strike outside Baghdad airport early Friday.

His death marked a dramatic escalation in tensions between the U.S. and Iran, which have often been at a fever pitch since Trump chose in 2018 to unilaterally withdraw Washington from a 2015 nuclear pact world powers struck with Tehran.

Iranian Supreme Leader Ali Khamenei, who bestowed the country's highest honor on Soleimani last year, vowed "severe retaliation" in response to his killing.

Trump said Saturday that if any Iranian retaliation strikes American targets or interests “we have targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD. The USA wants no more threats!"

Concerns have mounted that should the U.S. strike Iranian cultural sites, that would be a war crime under international law. But Trump has been undeterred, reiterating the threat Sunday.

“They’re allowed to kill our people. They’re allowed to torture and maim our people. They’re allowed to use roadside bombs and blow up our people. And we’re not allowed to touch their cultural sites? It doesn’t work that way,” he said.