US President Donald Trump said Thursday he would sign an order instructing the Department of Homeland Security to pay airport security officers who have been working without salary amid a budget standoff on Capitol Hill.

Many Transportation Security Administration (TSA) staff at the nation's airports have gone weeks without full pay.

"I am going to sign an Order instructing the Secretary of Homeland Security, Markwayne Mullin, to immediately pay our TSA Agents in order to address this Emergency Situation, and to quickly stop the Democrat Chaos at the Airports," Trump said on his Truth Social platform.

"It is not an easy thing to do, but I am going to do it!" Trump added.

US airports are struggling with long delays, with some passengers reporting waits of several hours during what is a busy spring travel period.

Unscheduled absences among TSA staff have surged to their highest levels since a shutdown of the TSA parent agency, the Department of Homeland Security (DHS), began in mid-February.

That ongoing dispute centers on demands by opposition Democrats for reforms of the Immigration and Customs Enforcement (ICE) agency, which has faced nationwide criticism of its aggressive tactics against undocumented immigrants and for the shooting deaths of two US citizens this year.

Trump has stymied hopes of agreement between Republicans and Democrats to end the budget standoff by saying he will not sign a funding deal unless Congress also passes a contentious bill to overhaul how citizens register to vote in US elections.

In his Thursday post, Trump implied that he would resort to his emergency powers as president to authorize the payment of TSA staff. But it remains unclear how that can be done as the power of the purse resides with Congress under the US Constitution.

In an attempt to reduce queues at airports, this week the Trump administration began deploying ICE agents to assist in providing security. ICE also comes under DHS but has funding under a separate government spending bill passed last year. 

The deployment has drawn sharp criticism from Democrats, rights activists and some Republicans, who warn ICE personnel are not trained for such work and that it risks escalating tensions in already stressed environments.