As concerns Major donors pledged on Sunday to give Afghanistan $16 billion in development aid through 2015 as they seek to prevent it from sliding back into chaos when foreign troops leave, but demanded reforms to fight widespread corruption.

Donor fatigue and war weariness have taken their toll on how long the global community is willing to support Afghanistan and there are concerns about security following the withdrawal of most NATO troops in 2014 if financial backing is not secured.

"Afghanistan's security cannot only be measured by the absence of war," U.S. Secretary of State Hillary Clinton told an international donors' conference in Tokyo.

"It has to be measured by whether people have jobs and economic opportunity, whether they believe their government is serving their needs, whether political reconciliation proceeds and succeeds."

The Afghan central bank has estimated that at least $6 billion a year in new investment from foreign donors will be needed to foster economic growth over the next decade.

Clinton also stressed the importance of Afghanistan - one of the most corrupt nations in the world - of taking aggressive action to fight graft and promote reforms.

President Hamid Karzai admits his government needs to do more to tackle corruption, but his critics say he is not doing enough, and some directly blame authorities for vast amounts of aid not reaching the right people.

"We have agreed that we need a different kind of long-term economic partnership, one built on Afghan progress in meeting its goals, in fighting corruption, in carrying out reform, and providing good governance," Clinton said.

CONDITIONS APPLY

U.S. officials provided no figure for their expected aid, but said the administration would ask Congress to keep assistance stable through 2017 compared with what Washington has offered over the past decade. Annual U.S. aid to Afghanistan has ranged from about $1 billion a decade ago to a peak of about $4 billion in 2010. It stands at about $2.3 billion this year.

Japan pledged $3 billion in aid for Afghanistan through 2016. Foreign Minister Koichiro Gemba said $2.2 billion of that amount would be grants for development projects in areas like investment in roads and infrastructure.

The EU has said it will continue with pledges of 1.2 billion euros a year, but warned that if progress is not made with rule of law and women's rights, this could be difficult to continue.

The pledges made in Tokyo are on top of the $4.1 billion by NATO and its partners for supporting the Afghan security forces.

Representatives from about 80 countries and international aid organisations, including the World Bank and the Asian Development Bank, gathered in Tokyo for the aid conference.

International donors provided $35 billion in aid to Afghanistan between 2001 and 2010, but the return on that investment has been mixed.

Afghanistan remains one of the five poorest nations. Major strides have been made in schooling children and improving access to health care, but three-quarters of the 30 million Afghans are illiterate and the average person earns only about $530 a year, according to the World Bank.

The government has identified several priority areas for economic development, including investment in agriculture and mining, which Western officials see as a possible engine for future growth. Afghanistan is believed to have up to a trillion dollars' worth of untapped mineral wealth.

Afghan Finance Minister Omar Zakhilwal said the Tokyo conference had shown aid donors were committed to the long haul. "Today's event sends the strongest message to Afghan people that the international community will be with us in 2014, 2015, 2017, 2020 and beyond," Zakhilwal told a news conference.

But World Bank Managing Director Sri Mulyani Indrawati said the pressure was on the Afghan government to deliver reforms and ensure fair elections in 2014 in order to secure aid beyond the amount pledged in Tokyo.

"This is a fragile conflict state," Indrawati told Reuters in an interview. "Three years is a very short time for a country to be able to build stable and competent institutions."

During a stopover in Kabul on Saturday, Clinton upgraded Afghanistan's security status to a major non-NATO ally, a largely symbolic move, aimed at reinforcing the U.S. message to Afghans that they will not be abandoned as the war winds down.

The new status may help Afghanistan acquire U.S. defence supplies and have greater access to U.S. training as the Afghan army takes more responsibility for the country's security ahead of the 2014 withdrawal of most NATO combat troops.