The United States plans to reduce its occupation troops in Afghanistan to 9,800 this year and to bring its military intervention to an end by the end of 2016, a senior official said Tuesday.

The United States plans to reduce its occupation troops in Afghanistan to 9,800 this year and to bring its military intervention to an end by the end of 2016, a senior official said Tuesday.

President Barack Obama was to announce the plan, which depends on the Afghan government agreeing to sign a joint security agreement with the US, later in the day.

"We will only sustain a military presence after 2014 if the Afghan government signs the Bilateral Security Agreement," the senior administration official told reporters.

"Assuming a BSA is signed, at the beginning of 2015, we will have 9,800 US service members in different parts of the country, together with our NATO allies and other partners," the official continued.

"By the end of 2015, we would reduce that presence by roughly half, consolidating US troops in Kabul and on Bagram Airfield.

"And one year later, by the end of 2016, we will draw down to a normal embassy presence with a security assistance office in Kabul, as we have done in Iraq."

Obama visited US forces in Afghanistan on Sunday, and spoke briefly by telephone with outgoing Afghan leader Hamid Karzai, who is due to step down this year after a June election.