US President Donald Trump has threatened to deploy troops to Baltimore, escalating a clash with Maryland Governor Wes Moore after the Democrat invited him to join a safety walk in the city.

If Wes Moore needs help, like Gavin Newsom did in L.A., I will send in the 'troops,' which is being done in nearby DC, and quickly clean up the Crime, Trump wrote on social media.

The comments mark the latest flashpoint in the president's efforts to deploy National Guard troops to Democratic-led cities as part of what he calls a crackdown on crime.

The use of military personnel for domestic law enforcement has drawn fierce backlash from Democrats. One governor described it as an abuse of power.

Trump has already deployed around 2,000 troops to Washington DC, a Democratic stronghold. On Sunday, the Guard started to carry weapons in Washington, the military said. Previously, their weapons were available if needed but kept in the armoury. A statement from the Joint Task Force said they were only to be used as a last resort.

As many as 1,700 troops are expected to mobilise in 19 states in the coming weeks, US media report.

Governor Moore, a frequent critic of the president's strategy, said Trump's comments about fighting crime come off as so, so tone deaf and so ignorant. It's because they have not walked our streets, Moore said. They have not been in our communities, and they are more than happy to keep making these repeated tropes about us.

Trump's Sunday Truth Social comments appeared to be a direct response to Moore's invitation letter to Trump which the president described as nasty and provocative.

In concluding, Trump suggested he would deploy troops in New York and Chicago as well, a plan that has led to condemnation from Democratic leaders across the states and locales who argue that such military interventions constitute an abuse of authority.