5,500 US troops in Afghanistan beyond 2016 'enough': Pentagon

US Secretary of Defense Ash Carter speaks during a briefing at the Pentagon in Washington D.C., capital of the United States, Oct 15, 2015. [Photo/Xinhua]

WASHINGTON - The Pentagon said on Thursday keeping 5,500 US troops in Afghanistan into 2017 would be enough, as US President Barack Obama broke his promise to bring all US troops home before leaving office.

"We do look at it as enough. We did a lot of homework on this," said US Secretary of Defense Ash Carter at a briefing.

"We are adjusting our presence based on conditions on the ground to give the United States and our allies the capability to sustain a robust counterterrorism platform, denying a safe haven for terrorists and violent extremist organizations."

Obama announced plans Thursday to keep 5,500 US troops in Afghanistan into 2017, and to maintain the current 9,800 forces through "most of 2016."

Calling the new plan "modest but meaningful," Obama said the US troops in Afghanistan will remain focused on training Afghans and counterterrorism operations against remnants of al-Qaida.

Echoing Obama, Carter said counterterrorism would be a part of the "enduring mission" in Afghanistan.

"Whatever it takes to protect our country and make sure that Afghanistan doesn't again become a platform from which terrorism arises," said Carter.

Obama had previously planed to reduce the current level of 9,800 US troops in Afghanistan to around 5,500 by the end of 2015 and withdraw all troops by the end of 2016 when Obama's presidency comes to an end.

Earlier this year, after a meeting with visiting Afghan President Ghani here, Obama announced no reduction of the current 9,800 US troops stationed in Afghanistan will occur through the end of 2015.