President Trump took a swipe at Speaker of the House Nancy Pelosi Thursday by denying her use of a military plane and postponing an imminent trip abroad, one day after she asked him to postpone his State of the Union address.

Mr. Trump told the new House speaker in a publicly released letter — less than an hour before she and other House Democrats were scheduled to leave — that he was postponing the trip to Brussels and Afghanistan to visit troops "due to the shutdown." Pelosi and other Democrats were preparing to load buses to take them to Joint Base Andrews for the trip, where they were scheduled to use U.S. military transportation. Mr. Trump has the authority to halt such military aircraft, senior White House officials said. In his letter, Mr. Trump suggested Pelosi could still use commercial transportation for the trip to visit troops.

Pelosi wrote to the president on Wednesday asking him to delay his State of the Union address, as the ongoing government shutdown would mean federal law enforcement officers would be working the event without pay. Mr. Trump did not specifically respond to Pelosi's State of the Union address request in his letter, and a senior White House official claimed the president's letter is unrelated to Pelosi's request.

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"Due to the shutdown, I am sorry to inform you that your trip to Brussels, Egypt, and Afghanistan has been postponed," Mr. Trump wrote. "We will reschedule this seven-day excursion when the shutdown is over. In light of the 800,000 great American workers not receiving pay, I am sure that you would agree that postponing this public relations event is totally appropriate."

The speaker's trip was a closely held secret, and a source familiar with the delegation's planning argued it was irresponsible and reckless for Mr. Trump to tell the world Pelosi was headed to a war zone — particularly since the president was just in Iraq and saw how much care had to be taken to keep the trip secret and secure. A senior White House official, however, said the administration sees no security risks, since the trip isn't happening.

While hundreds of thousands of federal employees are affected by the shutdown, the Pentagon is a fully funded department for the rest of the fiscal year.

Trump's letter to Nancy Pelosi

A senior White House official claimed Mr. Trump made the decision because he wants Pelosi in Washington to negotiate.

"She should not leave the country for seven days in the middle of a government shutdown," the official said. "She's the person on her side that has to be present to make a deal."

A senior White House official told CBS News the Pentagon was informed of the postponed trip before Pelosi was.

Meanwhile, a number of high-profile Trump administration officials will be heading to Davos, Switzerland, for an economic forum next week, and Mr. Trump himself made a trip to Iraq to visit troops over the Christmas holiday.

House Majority Leader Steny Hoyer called Mr. Trump's decision to call off the military plane "beneath any president of the United States to take," noting Pelosi is third in line to the presidency.

"The actions of the president were petty, mean-spirited, and beneath any president of the United States to take," Hoyer told reporters. "Doing this small, petty act is unfortunately all too regular for this president."

Sen. Lindsey Graham called it "inappropriate" for the president to cancel Pelosi's trip to visit troops.

"One sophomoric response does not deserve another," Graham wrote in a statement. "Speaker Pelosi's threat to cancel the State of the Union is very irresponsible and blatantly political. President Trump denying Speaker Pelosi military travel to visit our troops in Afghanistan, our allies in Egypt and NATO is also inappropriate."

Ed O'Keefe and Fin Gomez contributed to this report.