U.S. Marines stand guard during the change of command ceremony at Task Force Southwest military field in Shorab military camp of Helmand province, Afghanistan, Monday, Jan. 15, 2018.

U.S. Marines stand guard during the change of command ceremony at Task Force Southwest military field in Shorab military camp of Helmand province, Afghanistan, Monday, Jan. 15, 2018. AP Photo/Massoud Hossaini

The bewildering message came just hours after his national security advisor said the United States would draw down to 2,500 by 2021.

All U.S. troops currently serving in Afghanistan will return to the United States by Christmas, President Donald Trump said in a shocking tweet Wednesday night just hours after his national security advisor said that the United States would draw down its forces in Afghanistan to 2,500 by early next year.

“We should have the small remaining number of our BRAVE Men and Women serving in Afghanistan home by Christmas!” Trump tweeted, about 90 minutes before the vice presidential debate was scheduled to begin.

Trump and other officials previously have said that the number of United States troops in Afghanistan would be down to between 4,000 and 5,000 troops around November, and that any subsequent withdrawal would be conditions-based.

But Trump has made it clear that he wants the United States out of Afghanistan, rarely speaking publicly about what “conditions” would be necessary to carry out that withdrawal and instead emphasizing the length of the conflict and complaining that U.S. soldiers are acting as “police” in the war torn country. Former and current administration officials have described him as eager to pull out by November in order to fulfill a key campaign promise from the 2016 election.

It was not immediately clear on Wednesday evening whether he had issued an order to zero out U.S. troops in Afghanistan by the end of the year. Notably, there have been no following statements or comments from U.S. officials at the Pentagon, U.S. Central Command in Tampa, Fla., or in Kabul. Typically, major changes to U.S. force levels or strategy in Afghanistan have been announced with coordinated public messages by administration and military leaders. Earlier in the day, National Security Advisor Robert O’Brien said that there are currently fewer than 5,000 troops in Afghanistan, and that the United States planned to draw down to 2,500 by early 2021.

“Ultimately, the Afghans themselves are going to have to work out an accord, a peace agreement,” O’Brien said at the University of Nevada, Las Vegas. “It’s going to be slow progress, it’s going to be hard progress, but we think it’s a necessary step – we think Americans need to come home.”

Over the past six months, the United States reduced the number of its troops in Afghanistan first to about 8,600, in accordance with a deal brokered with the Taliban and signed in February. That deal envisioned the immediate drawdown from 14,000 to 8,600 troops by the summer, and a complete U.S. withdrawal within 14 months, if the Taliban lived up to their end of it. Pentagon leaders have long insisted that the second phase would be “conditions-based.”

Defense officials have long braced for the possibility that Trump, frustrated with the slow pace of the withdrawal process, may order a sudden and complete exit, as he did for U.S. troops in Syria. Trump has repeatedly sought to withdraw the military from conflict zones and permanent stations overseas, arguing that Americans are tired of “endless” wars. As the weeks wind down the 2020 election, the president has urged or ordered further withdrawals from Iraq, Germany, and elsewhere, in an attempt to fulfill a campaign promise to end the so-called “forever” wars and force allies to take on more of the burden of their own security.

Frustration with the lengthy Afghanistan war — in which 2,400 Americans and thousands more coalition troops and Afghan citizens have perished — has grown into a national mood in recent years. Throughout the Democratic primary campaign, presidential candidates including presumptive nominee Joe Biden called for either an outright withdrawal or a substantial drawdown.

Wednesday marked the 19th anniversary of the U.S. invasion of Afghanistan to topple al Qaeda in 2001.