The blood and treasure sacrifices of the past could be wasted without investment in Afghanistan's civil society when foreign combat forces leave, a world donors' conference in Tokyo was told on Sunday.

UN chief Ban Ki-moon, who is among key global figures gathering in the Japanese capital for talks on a "Transformation Decade", said progress in security and broad-based development had been made, but remained "fragile".

"Failure to invest in governance, justice, human rights, employment and social development could negate investment and sacrifices that have been made over the last 10 years," he told the meeting.

Sunday's conference is aimed at plugging the gap between what Kabul gets from its barely-functioning economy and what it needs to develop into a stable country.

Afghan President Hamid Karzai, who is in Tokyo along with US Secretary of State Hillary Clinton and United Nations chief Ban Ki-moon, has called for $4 billion a year in civilian aid.

On Saturday Japan announced donors will stump up more than $16 billion in civilian aid for four years to 2015.

"We are at a critical moment in Afghanistan's history in transition from reliance on the aid that has enabled the country's institutions to take roots to a normalised relationship of a sovereign, functioning Afghanistan with its people and with its international partners," Ban said.

Clinton, who on Saturday said the United States had designated Afghanistan a major non-NATO ally, told the meeting peace on its own was not a sufficient dividend for the sacrifices that have been made.

"We all know that Afghanistan's security will not be measured only by the absence of war. It will also be measured by the presence of jobs and economic opportunity," she told the meeting.

She said the administration of US President Barack Obama would be asking Congress to agree to keep American civilian assistance to Afghanistan at or near current levels until 2017.

In his opening remarks to the conference, Karzai said his country had come a long way, but acknowledged security remained a major problem.

"Afghanistan continues to face grave risks from common threats, not only terrorism and extremism. The peace and reconciliation process is of particular urgency at the present time."

"(The) responsibility to make Afghanistan peaceful and self-reliant is primarily our own as Afghans. We will remain steadfast in our commitment in this historic partnership."

Kabul covers only a third of the $6 billion it spends each year, not counting security costs, and has for a long time been heavily dependent on aid.

There are fears that once the US and its allies no longer have to worry about their soldiers dying in Afghanistan after the 2014 pullout, the country could be left to drift into the hands of drug lords and extremists.

Representatives from more than 80 nations and international organisations gathering in the Japanese capital are expected to adopt the "Tokyo Declaration", pledging support and cash for Kabul.

As part of the so-called "Transformation Decade" from 2015, participants will issue a framework document stressing the principle of "mutual accountability", offering aid on the condition that Kabul clamps down on endemic corruption.

According to the World Bank, spending on defence and development by foreign donors accounted for more than 95 percent of GDP in 2010-11.

In May an Afghanistan security conference in Chicago involving the countries of the NATO-led coalition adopted a plan to provide $4.1 billion in annual security aid in coming years.

The focus in Tokyo is on development.

In an interview with the Asahi Shimbun newspaper published Friday, conference co-chairman Gemba said he was hoping it would result in pledges worth at least $3.0 billion a year.

But he warned the money would come with strings.

"(Kabul) must improve its governance capacity, including eradicating corruption," he said, adding a mechanism to review progress in these areas every two years had to be developed.