An airman observes an Army CH-47 Chinook helicopter at an undisclosed location in Afghanistan, Feb. 9, 2018.U.S. Army photoWASHINGTON — President Donald Trump, who campaigned in 2016 on ending “ridiculous endless wars” in the Middle East, took to Twitter on Wednesday to announce that American forces currently serving in Afghanistan will be home by Christmas.It was unclear if Trump, who is seeking re-election next month, was giving an order via tweet or reiterating a long-held campaign promise in order to appeal to voters.The Taliban welcomed Trump’s announcement, saying it was a positive step toward a peace agreement.Earlier this year, the United States brokered a peace deal with the Taliban that would usher in a permanent cease-fire and reduce the U.S. military’s footprint from approximately 13,000 to 8,600 by mid-July. And by May 2021, all foreign forces would leave the war-torn country.Trump’s tweet Wednesday came on the 19th anniversary of the start of the war in Afghanistan, which has dragged on to become America’s longest conflict.Earlier on Wednesday, Trump’s national security advisor gave a more conservative timeline for reducing U.S. forces.”When President Trump took office, there were over 10,000 American troops in Afghanistan,” Robert O’Brien said in a national security speech at the law school of the University of Nevada, Las Vegas.”As of today, there are under 5,000 and that will go to 2,500 by early next year,” he said.The National Security Council, White House and Pentagon did not immediately respond to CNBC’s request for comment for clarity on the administration’s drawdown timeline in Afghanistan. Trump, currently confined in the White House for treatment after testing positive for coronavirus, has previously directed the Pentagon to reduce the U.S. fighting force in conflict zones. In 2018, Trump tweeted that the United States would be withdrawing troops out of Syria, a move that sent a shock wave through the Pentagon and contributed in part to the resignation of then-Defense Secretary James Mattis. Trump later reversed his decision to withdraw from Syria.In May, Trump complained on Twitter that America’s role in Afghanistan has been reduced to a “police force” and not a “fighting force.”When asked about the tweet by reporters during a White House event, Trump said that the U.S. could go back to Afghanistan if needed.”We can always go back if we have to. If we have to go back, we’ll go back, and we’ll go back raging,” Trump said in May.The collective wars in Afghanistan, Iraq and Syria have cost U.S. taxpayers more than $1.57 trillion since Sept. 11, 2001, according to a Defense Department report.The current U.S. military operations, designated Operation Freedom’s Sentinel in Afghanistan, Operation Inherent Resolve in Syria and Iraq, and Operation Noble Eagle, have accounted for $266 billion of that sum.Of the three current operations, Freedom’s Sentinel takes the lion’s share of costs at $193 billion.