"Due to the Shutdown, I am sorry to inform you that your trip to Brussels, Egypt, and Afghanistan has been postponed," Trump wrote in a sharply-worded letter released Thursday afternoon, the latest move in a memorable display of Washington political theater. "We will reschedule this seven-day excursion when the Shutdown is over."
White House press secretary Sarah Sanders tweeted out Trump's letter.
Trump added that he feels “it would be better” if Pelosi was in Washington negotiating with him “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,” Trump noted. “I look forward to seeing you soon and even more forward to watching our open and dangerous Southern Border finally receive the attention, funding and security it so desperately deserves.”
Pelosi spokesman Drew Hammill tweeted the first reaction from the speaker's office, calling the trip a "weekend visit to Afghanistan," while denying that a stop in Egypt was planned. Hammill further explained that the scheduled stop in Belgium was for "pilot rest" while the delegation was scheduled to meet with top NATO commanders and U.S. military leaders.
“The purpose of the trip was to express appreciation and thanks to our men and women in uniform for their service and dedication, and to obtain critical national security and intelligence briefings from those on the front lines,” Hammill said, adding that Trump traveled to Iraq, and New York Republican Rep. Lee Zeldin also led a congressional delegation to Iraq during the shutdown.
House Intelligence Committee Chairman Rep. Adam Schiff, a California Democrat who had planned to join Pelosi’s congressional delegation to Afghanistan, says Trump’s decision to derail the trip is “completely inappropriate.”
“We’re not going to allow the President of the United States to tell the Congress it can’t fulfill its oversight responsibilities, it can’t ensure that our troops have what they need whether our government is open or closed," Schiff told reporters after huddling with Pelosi in the speaker’s office.
Asked if the tit-for-tat brings negotiators any closer to a deal to end the shutdown, Schiff told ABC's Mary Bruce that “the shutdown is completely unnecessary from beginning to end.”
“Whether this fifth-grade conduct is going to continue, it's hard to see how it's rather constructive,” Schiff said. “At the end of the day, whatever his motivation is, we'll do our oversight.”
Schiff refused to say whether Pelosi would still make the trip and blasted the president for divulging the speaker’s travel plans.
“I'm not going to comment on the speaker's travel plans,” Schiff said. “Frankly, there has been far too much said about that already. And I think the president's decision to disclose a trip that the speaker is making to a war zone is completely and utterly irresponsible in every way.”
An administration official said that the Defense Department was made aware prior to the letter being sent to Pelosi Thursday and that the policy applies to all CODELs -- or congressional delegation trips -- that may have been scheduled during the shutdown.
Sanders, when asked why Trump sent the letter to Pelosi, said, “We want to keep her in Washington. If she leaves she guarantees that the second round of paychecks to workers won’t go out.”
She said Pelosi and Senate Minority Leader Chuck Schumer “always have an invitation” to the White House if they want to come to negotiate.
Asked if there is any White House response to Pelosi's letter to Trump on Wednesday calling for a delay in his State of the Union Address, she said, “We’ll keep you posted. Nothings changed on that front.”
Majority Leader Steny Hoyer called Trump's letter “a petty move," adding it is "unworthy of the President of the United States.”
South Carolina Republican Sen. Lindsey Graham, a frequent Trump ally, released a statement calling the back-and-forth "sophomoric."
“One sophomoric response does not deserve another. 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," Graham said.
“I am glad the Speaker wants to meet our troops and hear from our commanders and allies. I am very disappointed she’s playing politics with the State of the Union," he continued. “I wish our political leadership could find the same desire to work for common goals as those who serve our nation in uniform and other capacities.”
Earlier Thursday, with the shutdown in its 27th day, Pelosi said she had not received a response to her letter, which urged Trump to delay the annual address until after government is reopened. When asked what she'd do if Trump were to insist on sticking to the Jan. 29 date, Pelosi she’d “cross that bridge when we come to it.”
“We haven't heard. Very silent more than 24 hours,” Pelosi said, seemingly amused. “Have you heard? We haven't heard.”
At the Pentagon Thursday morning, Trump continued to push for border security, including his proposed border wall, accusing Pelosi of refusing to let Democrats negotiate.
“The federal government remains shut down because congressional Democrats refuse to approve border security," Trump said. "We're going to have border security.”
Pelosi and Trump haven’t spoken to each other since Trump walked out of a Jan. 9 meeting with congressional leaders in the Situation Room, declaring it “a total waste of time.”
Last year, Trump delivered the State of the Union to a televised audience of 45.6 million people, leaving the impression that Pelosi is denying the president a prime platform to share his point of view as leverage against the president.
“Let's get a date when government is open. Let's pay the employees,” Pelosi said. “He thinks it is okay not to pay people who do work. I don't. My caucus doesn't either.”
Pelosi said she is confident security professionals could keep the event safe, but added her qualm is that they would not be immediately paid for their work.
“This is directly related to our security,” Pelosi said, recounting several votes the House has taken to end the shutdown.
Pelosi predicted there's “bipartisan agreement” to use other technology to protect the border, but stressed “I'm not for a wall,” when she was asked why she hasn’t proposed an alternative dollar figure to counter the president’s $5.7 billion demand for a barrier.
“The president says the only way to do it is with a wall. That's a debate that we have,” Pelosi said. “We must respect our workers protect our borders and reopen government the government immediately.”
ABC News' Alexander Mallin and Mariam Khan contributed to this report.