The White House says it will likely lay off at least 10,000 federal workers during the US government shutdown as Republican President Donald Trump steps up pressure on Democrats.

The shutdown has ground into its third week, with Congress deadlocked in a clash over spending and Trump following through on his threats to take a hatchet to the workforce in response.

“I think we’ll probably end up being north of 10,000,” White House Office of Management and Budget chief Russ Vought said.

“We want to be very aggressive where we can be in shuttering the bureaucracy.”

Court documents filed by the Department of Justice showed that more than 4000 employees were fired on Friday, with the US Treasury and health, education and housing departments hardest hit.

Vought said that was a “snapshot” and that there would be more.

Trump has warned that continued refusal by Democrats to support a House-passed resolution to fund the Government through late November would result in mass layoffs targeting workers deemed to be aligned with the opposition party.

The US President has vowed to find a way to pay troops due to go without their paycheques for the first time, although the uncertainty is already leading to long lines of men and women in uniform at food banks.

- Agence France-Presse