Washington (CNN) Saudi Arabia has paid the US approximately $500 million to begin to cover the cost of US troops operating in the country, according to a US 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 US 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 US believes the Saudis owe.

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