The Obama administration will ask Congress to sustain US assistance for Afghanistan through to 2017 as part of the international effort to stabilise the country.

US Secretary of State Hillary Clinton made the pledge on Sunday as some 70 countries gathered in Tokyo to announce a four-year civilian assistance plan. Altogether they are promising to give $US16 billion ($A15.6 billion) to Afghanistan through to 2015.

Most international forces will pull out of the country over the next two years.

The US funds will help Afghanistan build its economy and make necessary reforms, Clinton said, adding that the Obama administration would ask Congress to sustain assistance near the average amount it has been over the last decade.

“We have to make the security gains and the transition irreversible,” Clinton told officials, including Afghan President Hamid Karzai.

She said Afghan security “cannot only be measured by the absence of war”.

“It has to be measured by whether people have jobs and economic opportunity; whether they believe the government is meeting their needs.”

Clinton said Afghanistan has made substantial progress over the last decade, but needs effective collaboration between its government, private sector, neighbours and international donors “so that this decade of transformation can produce results”.

Annual US civilian assistance since 2001 has ranged from $US1 billion to this year’s high of $US2.3 billion.

Clinton said the aid request to Congress through to 2017 would be to maintain funding at or near the average level, without specifying further.