Obama said leaving more troops in Afghanistan when he leaves office will also give the next USA president more flexibility to make decisions about how to best move forward on the long-running conflict. Obama repeated his vow that he would not allow Afghanistan to be used as a safe haven for terrorists.
The president highlighted recent successes by Afghan forces against the Taliban but acknowledged that the security situation in the country remains precarious.
His original plan was to draw down US troops in Afghanistan to 5,500 by the end of this year. But a Taliban resurgence has forced Washington to rethink its exit strategy.
The U.S. now has around 9,800 troops in the country. " ... For all of the bluster about funding troops in harm's way, it is the President who proposes to extend the vital mission without any resources behind it".
The new drawdown plan was announced, and also reinforced the probability that the United States will remain inside of Afghanistan for years to come.
Obama's presidency ends in January.
For all of the North Atlantic Treaty Organisation countries that are in Afghanistan, the key issue often isn't as much US strategy as it is, Is the USA staying? suggested Cordesman. "You've been unable to prevail", he said. "Our resolve is high and our determination is firm".
And compared to their previous mission, helping to lead the fight, our forces are now focused on two narrow missions: "training and advising Afghan forces and supporting counter terrorist operations against the remnants of al Qaeda as well as other terrorist groups, including ISIL", Obama said.
Less than three years later, the Islamic State swept into Iraq from its strongholds in Syria, encountering little resistance from USA -trained Iraqi security forces who abandoned their equipment and fled.
Republican leaders in Congress were welcoming the decision, but criticizing Mr. Obama for not keeping even more there.
Obama said he had made the decision after a lengthy internal debate, and based on a recommendation from the new USA commander in Afghanistan, General John W. Nicholson.
In announcing the "additional adjustment to our posture", Mr. Obama said Afghan security forces are "still not as strong as they need to be". "All of us have a vital interest in the security and stability of Afghanistan".
And far from predicting a swift de-escalation of USA troop deployments overseas, Obama, who once told Americans that "the tide of war is receding", appeared to lay the ground for prolonged US involvement.
But with only a few months left in office, Obama will likely have a hard time securing long-term commitments. Obama also pointed out that 38 Americans had died in the past 18 months.
The first USA troops went into Afghanistan in October 2001, he said, and attacked al Qaeda.
Obama's plan still calls for a reduction in U.S. troop levels from the current roughly 9,800, but not as much as previously planned.
Ghani's efforts to get the Taliban to engage in peace talks have been mostly fruitless, and the Afghan public has started losing patience as security worsens.
"Afghanistan is not a ideal place", Obama said, adding that it was one of the poorest countries in the world.
Obama spoke in advance of a North Atlantic Treaty Organisation summit on Friday and Saturday in Warsaw, Poland, where alliance members are expected to confirm their support for the Kabul government.