Washington (CNN) President Donald Trump said Thursday he was denying House Speaker Nancy Pelosi a military plane for a trip to Afghanistan that was set to begin in the afternoon, a tit-for-tat retaliation that deepened the divide between the leaders and brought the government no closer to reopening.

The move, apparently in response to Pelosi's letter a day earlier suggesting the President reschedule his State of the Union address, made for high drama but little substance in the ongoing standoff over border security.

As the partial government shutdown stretches nearly a month , the back-and-forth reflects a West Wing angling for the upper hand in a stalemate with newly powerful Democrats.

Pelosi had been scheduled to leave within the hour that Trump's letter was made public, making for the awkward site of a large blue Air Force bus idling outside the Capitol as the implications of the President's missive came into focus.

The administration "worked with the Air Force and (the Defense Department) and basically took away the rights to the plane from the speaker," one White House official said.

The White House released Trump's letter to Pelosi a day after she suggested the President postpone his planned State of the Union address, scheduled for later this month, until the government shutdown is resolved.

"Due to the Shutdown, I am sorry to inform you that your trip to Brussels, Egypt, and Afghanistan has been postponed," Trump wrote Pelosi on Thursday. "We will reschedule this seven-day excursion when the Shutdown is over."

Later, Pelosi's spokesman said the stop in Brussels was mainly to allow the pilot to rest and that Egypt was not on her itinerary.

Even though Afghanistan -- an active US combat zone -- was one of the countries on her planned itinerary, Trump suggested she fly commercial.

"Obviously, if you would like to make your journey by flying commercial, that would certainly be your prerogative," Trump wrote.

The President has the authority to direct the Defense Department to not use military assets to support a congressional delegation to military theaters. That includes air transport and additional security procedures.

White House officials, including acting chief of staff Mick Mulvaney, began discussing canceling Pelosi's trip early Thursday morning, according to two people with knowledge of how the day unfolded. Aides felt caught off guard when Pelosi publicly released her letter calling on Trump to postpone his State of the Union address, or deliver it in writing, and felt canceling the military air travel would be an ideal response.

Trump's penned retort amounted to his first public response to Pelosi's Wednesday letter, in which she suggested "we work together to determine another suitable date after the government has re-opened" for the State of the Union address.

Trump and his aides -- loathe to abandon a key evening of presidential messaging yet intrigued by a new opening to break tradition -- have yet to strike on a path forward for the State of the Union speech. Trump's letter to Pelosi did not address the scheduling of his address to Congress. And it did not offer any new incentives to return to negotiations on reopening closed-down agencies.

A Pelosi spokesman responded to Trump's letter pointing out the President's own shutdown trip to Iraq as well as one by Republican lawmakers.

"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," Pelosi spokesman Drew Hammill tweeted. He said the stop in Brussels was also to have included meetings with NATO leadership.

SOTU impasse

Democrats responded angrily to the move.

"All too often in the last two years, the President has acted like he's in the fifth grade. And to have someone who has that kind of character running the country is an enormous problem at every level," said Rep. Adam Schiff, the House Intelligence Committee chairman who had been due to travel with the speaker.

As the drama unfolded, even some Republicans lamented a broken state of affairs.

"One sophomoric response does not deserve another," Sen. Lindsey Graham, a top GOP ally of the President's, wrote in a statement.

Sen. John Cornyn, a member of Republican leadership, bemoaned "too much childishness" in the shutdown fight between Trump and Pelosi.

Just as Pelosi pointed to security officials working without pay as a reason to delay his State of the Union address, Trump said he was postponing Pelosi's trip "in light of the 800,000 great American workers not receiving pay."

Trump also used the letter to jab at some of the time Pelosi has spent outside of Washington during the shutdown, saying that "it would be better if you were in Washington negotiating with me and joining the Strong Border Security movement to end the Shutdown."

Trump has expressed confusion at why his attempts to pressure Democrats for border wall funding have yielded no progress. Meanwhile, some of his advisers worry the mounting consequences for unpaid federal workers could further erode support for Trump's cause.

The State of the Union address, initially scheduled for January 29, was viewed as a potential turning point. One White House official said the administration had begun putting together a list of potential invited guests in the first lady's box, including some "angel families" of people killed by undocumented immigrants.

Those plans were thrown into flux on Wednesday when Pelosi wrote Trump, citing concerns over security during the shutdown, which has forced Secret Service employees to work without pay.

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Upon receiving the letter, White House aides were initially unsure of how to proceed, people familiar with the matter said. The White House is weighing alternatives for the venue and style of Trump's State of the Union, but doesn't appear to have settled on a plan just yet, the people said.

GOP Rep. Mark Meadows, a close ally of the President's who is in frequent touch with the White House, said Thursday he believed Trump will deliver the speech outside the House Chamber.

"I think he'll give the State of the Union somewhere else, and Nancy's politics will come back to bite her," he said.

Trump himself viewed Pelosi's the letter as a political stunt, according to a person who discussed it with him. He did not raise it during a lunch meeting with lawmakers on Wednesday, and did not appear overly incensed by the move.

Some inside the West Wing have viewed Pelosi's letter as an opportunity to finally break the traditional State of the Union mold -- something previous White Houses have mulled but ultimately decided against. Others, however, are not in favor of a nontraditional State of the Union. And most believe they need more clarity from Pelosi before proceeding.

One Trump adviser told CNN's Jim Acosta part of the betting around the deliberations is that Pelosi will "fold" and allow Trump to deliver his speech in the House of Representatives. The adviser described the battle between Trump and Pelosi as "King Kong versus Godzilla."

Optics

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Some advisers have pushed Trump to deliver the annual address from the Oval Office in order to continue projecting the message that he is sitting in the White House, waiting for Democrats to make a deal. That's an argument the President has repeatedly pressed over the past weeks to little avail.

However, a prime-time address delivered from the Oval Office earlier this month fell flat, a memory that could deter the President from selecting the audience-less venue for an annual tradition he actually likes to observe.

Trump told people last week he disliked the address to the nation he delivered from the Oval Office, which he believed looked and sounded flat and lifeless. He told a group of TV anchors ahead of the speech he was unconvinced that it would change any minds, but allowed some of his advisers to talk him into it.

Before the speech he spent a long while -- more than is typical for a President, according to a person familiar with the setup -- with aides adjusting the camera framing and lighting so that it met his specifications.

Watching clips afterward, Trump was even more convinced it was a useless exercise. One person who was with him says he grimaced when he saw a clip on television, believing it looked stilted and robotic. He said he doubted it was worth the trouble. And polls seemed to prove him right -- a Quinnipiac University survey this week showed only 2% of respondents' minds were changed about the border wall by the speech.

"Nobody wins in a shutdown. Nobody does. A lot of Americans are hurt because of it," said Marc Short, Trump's former White House legislative affairs director and a CNN political commentator. "I do think that Democrats also risk the reality of when this is over, will Americans look at this and say there is one side pushing border security and one side wasn't?"

Alternative plans

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White House aides had already begun working on writing the State of the Union address, and had hoped to use it as an opportunity to hammer home the President's warning of an immigration crisis from the loudest megaphone he has.

With an address in the House Chamber thrown into question, some have suggested to the White House that Trump simply deliver the State of the Union speech from the Senate chamber instead, because the Republican-controlled upper body could invite the President rather than the Democratic-controlled House.

But as of Thursday there were no plans among Senate Republicans to invite the President to speak. And doing so would still require a 60-vote majority among senators, meaning some Democrats would have to come on board. A senior Republican congressional aide said the White House has not yet given guidance on any changes to its plan for the State of the Union.

The White House is also considering doing a rally-style State of the Union, which would be coordinated through Trump's campaign, a person familiar with the matter said. The idea is still preliminary, however, and formal plans have not been laid.

Many in Washington view the traditional State of the Union -- delivered in the House Chamber -- as a tired exercise. Aides to former President Barack Obama also considered taking the yearly speech on the road or delivering it in an alternative venue, though decided against it in the end.

Trump, however, has seen the speech as bolstering his presidential standing. He gained relatively positive reviews for his first two addresses to Congress, and enjoyed the applause that Republican lawmakers provided during his speeches.

For that reason, top aides are not moving forward with making firm alternative plans until they can gain some clarity from Pelosi about whether she has actually disinvited Trump from delivering the address.

As of Thursday morning it did not appear the two sides had spoken -- Pelosi said she'd received "no response" from the White House to her letter. During her weekly news conference, she denied she was attempting to withhold from Trump a high-profile venue to address Americans.

"I'm not denying him a platform at all," Pelosi said. "I'm saying, 'let's get a date when government is open.' "