WASHINGTON – President Donald Trump moved Friday to further limit travel by Congress members during the partial government shutdown, and said he would make a "major announcement" about border security on Saturday after weeks of mulling the declaration of a national emergency.

"I will be making a major announcement concerning the Humanitarian Crisis on our Southern Border, and the Shutdown, tomorrow afternoon at 3 P.M., live from the @WhiteHouse," Trump tweeted late in the day.

Trump has spoken in recent weeks about declaring a “national emergency” at the border, theoretically allowing him to use defense money for his proposed wall along the U.S.-Mexico border - but also triggering a lawsuit from Democrats who say the president lacks the legal authority for such a move.

The White House would not say whether Trump’s announcement would be an emergency declaration.

"I suggest everybody tune in," White House spokeswoman Sarah Sanders said.

Trump issued his cryptic tweet hours after his administration said it would bar members of Congress from using government planes without prior written approval.

The new policy, announced in a memo to department heads, was put in place one day after Trump canceled a military plane for House Speaker Nancy Pelosi, who was planning to lead a congressional delegation to Afghanistan this weekend.

"Under no circumstances during a government shutdown will any government owned, rented, leased or chartered aircraft support any Congressional delegation, without the express written approval of the White House Chief of Staff," wrote Russell Vought, acting director of the Office of Management and Budget.

"Nor will any funds appropriated to the Executive Branch be used for any Congressional delegation travel expenses, without his express written approval,” Vought’s memo said.



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As the government shutdown entered Day 28 on Friday, Trump taunted Pelosi over postponing her trip to Afghanistan, while Pelosi's office said it canceled a backup plan because administration leaks put travelers at risk.

"Why would Nancy Pelosi leave the Country with other Democrats on a seven day excursion when 800,000 great people are not getting paid," Trump tweeted a day after canceling the military plane that was to have taken the speaker and other Democratic lawmakers to the war zone in Afghanistan.

Adding in a complaint about immigration, Trump referred to Pelosi's home state of California by saying: "Could somebody please explain to Nancy & her 'big donors' in wine country that people working on farms (grapes) will have easy access in!"

Pelosi's office, meanwhile, said it also had to cancel a commercial trip to Afghanistan because the Trump administration leaked details of it, undermining security for the lawmakers who planned to go.

“In light of the grave threats caused by the President’s action, the delegation has decided to postpone the trip so as not to further endanger our troops and security personnel, or the other travelers on the flights," said Pelosi spokesman Drew Hammill.

Hammill also said: "The Congress has a constitutional responsibility to conduct oversight in the war zone where our men and women in uniform are risking their lives every day."

Sanders disputed Pelosi's claim that the administration leaked news of the commercial flight, saying it is “unbecoming of the speaker to make that type of accusation."

It is "outrageous that she would accuse the president of the United States of putting any life in jeopardy," Sanders said.

In any event, no meetings are scheduled between Trump and Pelosi to try to resolve the budget impasse at the heart of the shutdown.

Trump has spoken at length about declaring a national emergency on the border to free up money for his border wall, but he seemed to back off of the idea late last week. He played down the prospects of an imminent emergency declaration, saying that he wasn't "going to do it so fast."

"What we're not looking to do right now is [a] national emergency," he said at the time. "I'd rather not do it because this is something that Congress should easily do."

But that was before this week's battles over the State of the Union and congressional travel.

While some Republicans have said they would consider a Democratic plan to reopen the government now while wall negotiations continue, Trump claimed on Friday the party is united behind his hard-line approach.

"Never seen the Republican Party so unified," Trump tweeted. "No 'Cave' on the issue of Border and National Security."

Pelosi's office said her trip – which included a stop in Brussels for pilot rest and meetings with NATO leaders – was designed to get information on the U.S. military commitment in Afghanistan that Congress funds. Other lawmakers had been scheduled to join the speaker on the trip.

“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.

He also noted that Trump traveled last month to Iraq during the partial government shutdown, as did a Republican congressional delegation.

And just hours after Trump grounded Pelosi's plane, first lady Melania Trump boarded a military plane and flew to Florida for a vacation at Mar-a-Lago, the Trump family's estate.

The government shutdown – the longest in U.S. history – was triggered by Trump’s demand for $5.7 billion to build a wall along the U.S.-Mexico border. Pelosi and other Democrats are refusing to give him the money, arguing that a wall would be costly and ineffective.

The move to void Pelosi's Afghanistan trip came a day after the new House speaker sent the president a letter suggesting his State of the Union address – scheduled for Jan. 29 – be delayed or that he submit it in writing if parts of the government remain closed at the end of the month.

Trump has yet to respond about his State of the Union plans.

Sen. Lindsey Graham, a South Carolina Republican, criticized Trump for canceling Pelosi's plane, writing on Twitter that "one sophomoric response does not deserve another."

The White House also responded by saying Trump has canceled plans to send a presidential delegation to the World Economic Forum in Davos, Switzerland, next week out of concern for the 800,000 government employees who are furloughed or working without pay during the shutdown.

Trump already had decided against making the trip but had planned to send a team from his administration.

Meanwhile, Trump's re-election campaign is turning his spat with Pelosi into a fundraising pitch. In a letter to supporters on Friday, the campaign asks for donations of between $20.20 and $140 to send faux red bricks to Pelosi and Senate Democratic leader Chuck Schumer of New York telling them to build the border wall.