President Obama said the hard decision was made after continuous assessments of the situation on the ground with his national security team.
"Afghan forces are still not as strong as they need to be. They're developing critical capabilities -- intelligence, logistics, aviation, command and control. And meanwhile, the Taliban has made gains, particularly in rural areas."
The U.S. will maintain 9,800 troops throughout most of 2016. Starting from 2017, that number will come down to 5,500. President Obama stressed that the U.S. troops will only focus on two objectives.
"The mission will not change. Our troops will focus on training Afghans and counterterrorism operations."
Meanwhile, U.S. allies in Afghanistan are urged to work out their own plans to maintain a military presence after 2016, the original time set for a complete withdrawal.
In addition, President Obama promised to continue to support Afghan President Ashraf Ghani as political reforms are ongoing in Afghanistan.
The decision also means that he would not keep his campaign promise to end two wars in his tenure.
But President Obama is determined to finish the mission.
"As Commander-in-Chief, I will not allow Afghanistan to be used as safe haven for terrorists to attack our nation again."
Republican presidential candidates including former Florida governor Jeb Bush and New Jersey governor Chris Christie have voiced support for the decision.
Xiaohong, CRI, Washington DC.
