WASHINGTON, Aug. 21 (Xinhua) -- U.S. President Donald Trump said on Monday that a rapid exit of the U.S. troops from Afghanistan was "unacceptable" and his new Afghanistan strategy will shift from a time-based approach to one based on conditions on the ground.
Trump made the announcement in a prime-time address at 9 p.m. local time (0100 GMT, Tuesday) from Fort Myer in Virginia. He did not talk about the widely anticipated increase of U.S. troops in Afghanistan.
In the over-30-minute speech, Trump ruled out a quick withdrawal of the U.S. troops, saying that it would have unacceptable consequences and "create a vacuum" that the Islamic State and al-Qaida would fill.
The president's national address came after a lengthy meeting with his national security team at Camp David on Friday.
He also made it clear that he would not "talk about numbers of troops or our plans for further military activities."
Currently, there are about 8,400 U.S. troops and another 5,000 troops of the North Atlantic Treaty Organization (NATO) in Afghanistan to train and assist Afghan forces against the Taliban, and conduct counter-terrorism missions.
Ahead of Trump's speech, U.S. media expected the president to authorize the deployment of up to 4,000 additional troops to Afghanistan.
Instead of being specific on troop numbers, Trump outlined the pillars of his strategy for Afghanistan and the South Asian region, saying that the United States was focused on "killing terrorists," not nation building.
He said that the new strategy would be based on conditions on the ground, not timing.
While reassuring the Afghan government about the U.S. commitment of cooperation, Trump also warned that the U.S. support was "not a blank check."
"The government of Afghanistan must carry their share of the military, political and economic burden," said Trump.
Hailing Trump's speech, U.S. Defense Secretary Jim Mattis said that the president's strategy came after "a rigorous interagency review."
"I will be in consultation with the Secretary General of NATO and our allies - several of which have also committed to increasing their troop numbers," said Mattis in a statement released by the Defense Department later in the day.
The new Afghanistan strategy came at a time when senior U.S. officials warned of a dire security situation in Afghanistan.
In a congressional hearing in June, Mattis said the United States was still "not winning" the war in Afghanistan, the longest in U.S. history.
Trump, a long-time critic of how the United States is fighting the war in Afghanistan, announced a review of the U.S. strategy on Afghanistan soon after taking office in January.
Then U.S. President George W. Bush ordered a dispatch of U.S. troops to fight the war in Afghanistan in October 2001, after the 9/11 terrorist attacks.
Since then, about 2,400 U.S. forces reportedly have died in Afghanistan.