WASHINGTON (Reuters) - U.S. President Donald Trump on Thursday stopped House of Representatives Speaker Nancy Pelosi from using a military plane for an overseas trip, in a tit for tat after the Democratic leader’s suggestion he postpone the State of the Union address during the partial government shutdown.

Republican Trump told Pelosi in a letter that her trip to Belgium, Egypt and Afghanistan, which he derided as a “public relations event,” would be postponed, citing the shutdown that has entered its 27th day.

Pelosi had planned to visit U.S. troops in Afghanistan, with a stop in Brussels for meetings to reaffirm the United States’ “ironclad commitment” to NATO, spokesman Drew Hammill said. Egypt was not on the itinerary.

The weekend trip had not been announced before Trump released his letter. Lawmakers often do not publicize foreign trips before they occur for security reasons, particularly when the trips involve a war zone as in this case.

“Due to the shutdown, I am sorry to inform you that your trip to Brussels, Egypt and Afghanistan has been postponed,” Trump’s letter said.

Trump told Pelosi she could make the trip by flying commercial.

“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,” Hammill said in a Twitter post.

The U.S. House Speaker normally uses a military plane for overseas travel and it was on that basis that Trump, as commander in chief, appeared to be acting.

“He postponed her ability to use military air,” which must be approved by the Department of Defense, said White House spokeswoman Sarah Sanders.

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On Wednesday, Pelosi had written to Trump suggesting he postpone his Jan. 29 State of the Union address because of security concerns during the shutdown.

The government has been partially shut since Dec. 22, in a standoff triggered by Trump’s demand for $5.7 billion to fund a wall along the U.S.-Mexico border, which Democrats oppose.

Presidents traditionally deliver the nationally televised annual address, which lays out the administration’s goals for the year, in the House of Representatives chamber before a joint session of Congress and the majority of the Cabinet.

Pelosi said earlier on Thursday that she had not received a response from the White House, and Trump did not respond to the suggestion in the letter.

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 criticized 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.”