US President Donald Trump has postponed House Speaker Nancy Pelosi's upcoming trip to Brussels and Afghanistan, asking her to stay to negotiate an end to the partial US government shutdown.

The president was able to halt the trip by denying the use of military aircraft to Mrs Pelosi and a delegation.

On Wednesday Mrs Pelosi had urged Mr Trump to postpone his State of the Union address, amid political deadlock.

Mr Trump's move came on the 27th day of the US's longest-ever federal shutdown.

The Republican president wants $5.7bn (£4.4bn) of congressional funding to build a wall on the US-Mexico border, but Democrats have refused.

Mr Trump's cancellation of the trip emerged less than an hour before the Democratic speaker of the House of Representatives was scheduled to leave on Thursday afternoon, US media say.

White House Press Secretary Sarah Sanders shared the president's letter in a tweet.

"I also feel that, during this period, it would be better if you were in Washington negotiating with me and joining the Strong Border Security movement to end the Shutdown," Mr Trump wrote.

The president added that Mrs Pelosi could proceed with the trip - which he described as a "public relations event" - using a commercial airline.

Later on Thursday the White House announced it would not send a US delegation to the World Economic Forum in Davos, Switzerland later this month, over the shutdown.

"Out of consideration for the 800,000 great American workers not receiving pay and to ensure his team can assist as needed, President Trump has cancelled his delegation's trip to the World Economic Forum in Davos, Switzerland," Mrs Sanders said in a statement.

Mr Trump had previously said he would not attend, and on Tuesday announced a scaled-back delegation, which was to be led by Treasury Secretary Steven Mnuchin.

Drew Hammill, Mrs Pelosi's deputy chief of staff, said her travel to Afghanistan had required a stop in Brussels to allow pilots to rest, as well as to meet top Nato commanders "to affirm the United States' ironclad commitment" to the alliance.

Mr Hammill said the plans did not include a visit to Egypt, and noted that Mr Trump and Republicans have travelled during a shutdown.

Mrs Pelosi's travel had not been announced before Mr Trump's letter.

Some commentators expressed dismay that the president would reveal plans about a trip to a war zone by a congresswoman who is third in line to the presidency.

The zero-sum battle drags on

Analysis by Anthony Zurcher, BBC News

The shutdown chess match between Donald Trump and Nancy Pelosi has turned into a game of checkers.

The House speaker threatens to take away his State of the Union Address? The president erases her congressional trip to Afghanistan.

Jump-jump-jump. Your move.

The White House had reportedly been caught flat-footed by Ms Pelosi's State of the Union announcement on Wednesday and was searching for ways to circumvent the speaker's threatened roadblock.

There's still no obvious solution for them, but that hasn't kept the president from firing back.

How the American public perceives this tit-for-tat is an open question.

At least so far, the president appears to be shouldering the lion's share of the blame for the government shutdown.

At some point, however, the governmental dysfunction could drag everyone down.

Meanwhile, 800,000 federal employees continue to work - or sit at home - without pay.

Government websites crash, services grind to a halt and the economic toll begins to mount.

This has become a zero-sum battle where the costs of continuing to fight are matched only by the political price to be paid if a side backs down.

House Majority Leader Steny Hoyer told reporters Mr Trump's action "demeans the presidency" while Republican Senator Lindsey Graham called Mrs Pelosi's threat to cancel the state of the union address "irresponsible" and Mr Trump's response "also inappropriate".

A White House aide told US media that the trip "would have guaranteed" that federal workers would miss their second paycheque "because [Mrs Pelosi] would not have been here to negotiate any kind of deal".

However, Mr Trump has not banned Mrs Pelosi from going - just from using military aircraft.

Fox News also reports that members of Congress who were due to join the trip have been left sitting on a US Air Force bus at Capitol Hill as staff at the Capitol, State, Pentagon and White House scramble to handle the situation.

In her own letter to Mr Trump on Wednesday, Mrs Pelosi called on him to reschedule his annual address to Congress since "the extraordinary demands presented" by the event could not be met during the shutdown.

Mr Trump has not yet directly responded to the request to move his speech, but in an email to campaign supporters, he said he was "disinvited" from his address to the American people.

Earlier on Thursday, Ms Pelosi told reporters that the Democrats did not want security officers working unpaid.

"Maybe he thinks it's okay not to pay people who work," Ms Pelosi said. "I don't."

Democrats in the House passed another bill to re-open parts of the government, but like past attempts, it is expected to fail in the Republican-led Senate.

The new stopgap bill proposes to re-open the government through 28 February.

Senate Majority Leader Mitch McConnell has refused to take up any legislation that does not have the president's approval, and has accused Democrats of wasting time.