US President Donald Trump is stepping up his fight with the Democrats in the US Congress over funding for a border wall that led to a government shutdown.
He postponed an overseas trip by House Speaker Nancy Pelosi, which would have included a visit to Afghanistan, saying it would be inappropriate while 800,000 federal workers were not receiving pay.
The move is widely seen as retaliation for Mrs Pelosi's suggestion that he reschedule his State of the Union address.
The rising tension suggested that the shutdown, now in its 27th day, remains far from being resolved.
Mr Trump has also cancelled his delegation's trip to the World Economic Forum in Davos, Switzerland, next week due to the shutdown, press secretary Sarah Sanders said in a statement.
The president attended last year's Davos event and had planned to go again this year.
Treasury Secretary Steven Mnuchin and Secretary of State Mike Pompeo were expected to lead the American delegation in his place.
Ms Pelosi had been scheduled to travel on a military aircraft as part of a congressional delegation to Belgium, where Nato is based, and Afghanistan to visit American troops stationed there.
In a letter denying her delegation the use of a plane, the Republican president called the trip an "excursion" but the Democrat's spokesman said the trip to the Afghanistan war zone was for security and intelligence briefings.
"In light of the 800,000 great American workers not receiving pay, I am sure you would agree that postponing this public relations event is totally appropriate," Mr Trump wrote.
Mr Trump told Ms Pelosi she could make the trip by flying commercial.
The president's intervention stopped the trip just as Ms Pelosi and other lawmakers were about to travel.
White House Press Secretary Sarah Sanders said Mr Trump had acted within his authority as commander in chief.
"He postponed her ability to use military air, which must be approved" by the Department of Defense, Ms Sanders said.
The decision appeared to be a response to a letter Ms Pelosi sent to Mr Trump, suggesting he delay the annual State of the Union address to Congress, scheduled for 29 January, to some point after the government reopens.
Ms Pelosi cited concerns over the capacity of the Department of Homeland Security and the Secret Service to safeguard the Capitol during the event. The agency later said it was capable of securing the venue.
Mr Trump's action drew criticism from one of his Republican allies in the Senate.
"One sophomoric response does not deserve another," Republican Senator Lindsey Graham wrote on Twitter.
He criticised Ms Pelosi's move on the State of the Union as "blatantly political" but said, "President Trump denying Speaker Pelosi military travel to visit our troops in Afghanistan, our allies in Egypt and NATO is also inappropriate."
Democratic Representative Elaine Luria, a first-year lawmaker and a 20-year Navy veteran, had harsh words for Mr Trump.
"The president's comment that lawmakers visiting Afghanistan is a public relations event is an insult to the brave men and women serving in harm's way," she said
Also on Thursday, the State Department said it would recall its employees and take steps to pay them salaries - a departure from other agencies.
"As a national security agency, it is imperative that the Department of State carries out its mission," Deputy Under Secretary of State Bill Todd said in a statement. "We are best positioned to do so with fully staffed embassies, consulates and domestic offices."
About one quarter of federal agencies have been shuttered since 22 December with Democratic lawmakers refusing to accede to Mr Trump's demands to pay for a wall along the US border with Mexico.
Mr Trump is holding out for $US5.7 billion for a border wall. Democrats, who took over the US House of Representatives this month, have rejected his demands, saying there are cheaper, more effective ways of enhancing border security.
Before leaving for the weekend, the House passed another bill that would fund the government through 28 February but the vote was later vacated and held over until next week after a procedural objection from Republicans.
The Senate, however, has refused to bring any funding bill to the floor for a vote that Mr Trump does not support.