Donald Trump has cancelled speaker of the House Nancy Pelosi‘s overseas trip to Brussels and Afghanistan, saying in a letter that he thinks it is best that she stay in Washington to continue discussions to reopen the federal government.

The president announced his decision in a letter to Ms Pelosi on Thursday, just a day after Ms Pelosi sent her own letter asking Mr Trump to either postpone his 2019 State of the Union, or else deliver it in writing because of security concerns posed by the shutdown.

“Due to the shutdown, I am sorry to inform you that your trip to Brussels, Egypt and Afghanistan has been postponed”, Trump wrote in his letter to the Democrat. “We will reschedule this seven-day excursion when the shutdown is over.”

In the letter, Mr Trump noted that Ms Pelosi could go ahead with her travels if she books flights through private or public options, but that she would not have access to the US military aircraft that are usually afforded to travelling American dignitaries and officials.

Mr Trump continued: “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. 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. Obviously, if you would like to make your journey by flying commercial, that would certainly be your prerogative.”

The US government has been partially shutdown for 27 days, making it the longest lapse in federal funding in US history.

Ms Pelosi had suggested on Wednesday, the president should postpone his State of the Union speech, citing the burden the shutdown has already placed on Secret Service agents who are not being paid but are required to work anyway.

The email exchange between Ms Pelosi and Mr Trump was met with criticism, even from one of the most ardent supporters of Mr Trump’s.

Republican Senator Lindsey Graham, who has become a key supporter of the president’s, said that Ms Pelosi’s letter was “very irrsponsible and blatantly political”. He also said that Mr Trump cancelling the speaker’s upcoming trip was “inappropriate”.

“One sophomoric response does not deserve another,” Mr Graham said.

​A spokesperson said that Ms Pelosi had planned her oveseas trip to Afghanistan in order to visit troops and to get security and US intelligence briefings. Drew Hammill, the deputy chief of staff for Ms Pelosi, disputed on Twitter that the speaker planned on making a stop in Egypt, and elaborated on the purpose of the congressional delegation (CODEL).

“The CODEL to Afghanistan included a required stop in Brussels for pilot rest. In Brussels, the delegation was scheduled to meet with top NATO commanders, U.S. military leaders and key allies–to affirm the United States’ ironclad commitment to the NATO alliance,” Mr Hammill wrote. “This weekend visit to Afghanistan did not include a stop in Egypt”.

He continued: “The purpose of the trip was to express appreciation & thanks to our men & women in uniform for their service & dedication, & to obtain critical national security & intelligence briefings from those on the front lines. The President traveled to Iraq during the Trump Shutdown as did a Republican CODEL led by [Representative Lee Zeldin]”.

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Some 800,000 federal workers have been furloughed or forced to work without pay as a result of the shutdown, leading to consirable concern among federal employees that a drawn out shutdown could leave them unable to pay their mortgage, for gas, for childcare, or for other necessities.

The impacts of the shutdown could be seen within weeks after it started on 22 December, with rubbish piling up in American national parks. But, it was just this past week, that the most severe consequence of the shutdown was felt among federal workers after many did not receive a scheduled pay cheque for the first time on Friday.

In addition to the impact on national parks, Transportation and Security Administration agents have reportedly been calling out of work sick at elevated rates, while federal prison workers have been showing up to work without pay in some of America’s most dangerous prisons.

Mr Trump and congressional leadership have met several times in the White House to negotiate an end to the showdown.