Underscoring the need for more rapid development of Afghan national security forces, President Barack Obama has given his Afghan counterpart Hamid Karzai a clear time line of 18 to 24 months to achieve the goals set by the US.

"President Obama underscored the need for more rapid development of the Afghan National Security Forces so that Afghans themselves can assume greater responsibility over the security of their country," the White House said in a statement.

The White House said Obama spoke to Karzai on the evening of November 30 via video teleconference for one hour about the way ahead in Afghanistan.

"The president also emphasised that US and international efforts in Afghanistan were not open ended and must be evaluated toward measurable and achievable goals within the next 18 to 24 months," the statement said.

Obama and Karzai reaffirmed their commitment to work closely together to ensure stability in Afghanistan and to prevent the country from becoming a safe haven for terrorists.

"They also discussed a range of related issues, including security, governance, corruption, economic development, and regional relations," it said.

Both the presidents agreed to redouble their efforts to improve the delivery of services to the Afghan people, particularly at the local level, and to reinvigorate economic development and investment, especially in the areas of agriculture, mining, water management, and energy.