Washington DC - President Donald Trump's contentious deployments of troops in multiple US cities cost nearly $500 million in 2025, according to an estimate from the nonpartisan Congressional Budget Office published Wednesday.

Trump sent troops onto the streets of Democratic-led cities, including Los Angeles and Washington DC, to quell allegedly out-of-control unrest, while court challenges blocked him from doing so in some other locations.

The deployments are set to cost tens of millions more per month this year.

"CBO estimates that those deployments...cost a total of approximately $496 million through the end of December 2025," its director Phillip Swagel wrote in response to a request from a top Democratic lawmaker.

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At $223 million, the costliest deployment has been the one in Washington DC, where there are still more than 2,600 National Guard personnel, followed by Los Angeles at $193 million, which saw a higher peak number of troops but for a shorter duration.

The cost of future deployments is "highly uncertain, mainly because the scale, length, and location of such deployments are difficult to predict accurately," Swagel wrote.

If current deployments are continued, "that cost would range from about $6 million a month for 350 personnel in New Orleans, to $28 million a month for 1,500 personnel in Memphis, to $55 million a month" for those in Washington, he added.

In addition to domestic deployments, Trump has repeatedly employed military force outside the US since returning to office for a second term a year ago.

In the Middle East, he ordered an air campaign against Yemen's Houthi rebels and strikes on Iranian nuclear sites.

Closer to home, US forces have targeted vessels off South America that Washington claims were smuggling drugs and seized the leader of Venezuela and his wife.