Saudi Arabia has paid the U.S. approximately $500 million to begin to cover the cost of US troops operating in the country, according to a U.S. official.

The payment was made in December last year. President Donald Trump asserted last week in an interview with Fox News that Saudi Arabia had “already deposited $1 billion in the bank.”

Earlier this week the Pentagon could not confirm that any payment had been made.

This is not the first time the Saudis have contributed to cover U.S. military costs. Saudi Arabia, Kuwait and other Gulf states paid $36 billion towards the costs of the Gulf War in 1990-91.

Bilateral talks are ongoing over precisely what expenses will be covered by the Saudis. That decision will lead to a final calculation on what the U.S. believes the Saudis owe.

“Consistent with the President’s guidance to increase partner burden-sharing, the Department of Defense has engaged Saudi Arabia on sharing the cost of these deployments, which support regional security and dissuade hostility and aggression. The Saudi government has agreed to help underwrite the cost of these activities and has made the first contribution,” said Cmdr. Rebecca Rebarich, Pentagon spokeswoman. “Discussions are ongoing to formalize a mechanism for future contributions that offset the cost of these deployments.”

The U.S. has deployed thousands of additional U.S. troops and missile defense batteries to Saudi Arabia in response to what Pentagon officials have said is an increased threat from Iran.

The Saudi funds are to cover the overall costs of deploying troops, as well as fighter jets and Patriot missile defense batteries to protect Saudi oil installations from Iranian missile and drone attacks. The deployments began after what the Saudis said were Iranian attacks on oil facilities in September 2019.

The Saudi embassy in Washington did not respond to CNN’s request for comment.

The U.S. and several European nations blamed Iran for a missile attack that targeted Saudi energy facilities temporarily affecting the country’s ability to produce oil.

The military buildup has come despite President Trump repeatedly claiming that he wants to reduce the U.S. military commitment in the Middle East, a pledge that he cited when he ordered the reduction of U.S. troops in Syria, a move that received broad bipartisan opposition in Congress, as many lawmakers see it as an abandonment of America’s partner in the fight against ISIS, the Kurdish-led Syrian Democratic Forces.

“In response to elevated threats in the Middle East over the past eight months, the Department of Defense has deployed U.S. military forces to the region to enhance U.S. defenses and augment Saudi air and missile defense of critical military and civilian infrastructure,” Rebarich said.

The ongoing discussions with the Saudis are aimed at formalizing a mechanism for future payments to offset the costs of deployments. But the Pentagon is insisting that future payments will not necessarily lead to the deployment of additional forces or taking on additional military missions.

Separately Saudi Arabia has partially reimbursed the U.S. for the cost of aerial refueling operations that the U.S. military provided to Saudi warplanes, according to the U.S. official.

The U.S. stopped providing aerial refueling to Saudi jets participating in its campaign against Houthi rebels in Yemen in November of 2018.

In December of 2018, the U.S. military said it was seeking a $331 million reimbursement from Saudi Arabia and the United Arab Emirates after discovering it had failed to properly charge the Saudi-led coalition fighting in Yemen for aerial refueling services.

The U.S. official said payments were made last year with the full amount likely to be paid soon.