When international donors meet in Tokyo on Sunday to chart Afghanistan’s economic future, they will be asked to pledge another decade of support in exchange for the Afghan government’s promises to clean up rampant corruption.

It won’t be the first time such vows are made, along with pledges to respect the rule of law and the rights of women and minorities. Similar conferences have been held in London, Kabul, Istanbul and Bonn in the last two years alone.

But it may be the last time the world is willing to believe them. With U.S. and NATO troops on their way out, maintaining Afghanistan’s fragile democracy and economy may seem less urgent, particularly without signs of real progress.

Despite years of U.S. pressure, Afghan President Hamid Karzai has failed to undertake significant reforms to curtail corruption, and there has not been a single high-level conviction in a corruption case. In recent months, the Obama administration has accepted that progress will continue to be slow and fitful.

The Tokyo conference, where Secretary of State Hillary Rodham Clinton will head the U.S. delegation, is the civilian-diplomatic bookend to NATO’s May summit. Meeting in Chicago, the alliance confirmed plans to withdraw foreign combat troops by the end of 2014 and pledged about $4 billion a year to pay for ongoing training, equipment and financial support for Afghanistan’s security forces.

In Tokyo, donors are expected to promise $3.9 billion in annual economic and development support at least through 2017 and ideally until 2025. The combined outlays equal roughly half of Afghanistan’s $15.9 billion gross domestic product last year, and the United States expects to contribute half the nearly $8 billion total.

“The numbers are relevant to some, but what’s more relevant is the idea that the international community is agreeing on the need for assistance, the need to keep investing in Afghanistan, and that the Afghans themselves are also taking responsibility for the things they need to do,” said a senior Obama administration official, speaking on the condition of anonymity in advance of the meeting.

The World Bank and the Afghan government worked together to come up with the $3.9 billion figure, along with a plan to set priorities to develop revenue-producing mines and other national resources, agriculture and education.

The money is a substantial decrease in the more than $100 billion a year the United States currently spends in Afghanistan. Without it, the administration and its partners fear Afghanistan will slip back to where it was two decades ago, when militant factions fought for control, the economy ceased to function and the Taliban emerged victorious.

“We have to convince our partners and the Afghans and ourselves that we are not leaving Afghanistan in the lurch,” Alex Thier, director of the Afghanistan and Pakistan office at the U.S. Agency for International Development, said Tuesday at a Brookings Institution conference.

But many think more funding will simply perpetuate the waste and corruption that have permeated Afghanistan during more than a decade of U.S. involvement.

Karzai is expected to outline new anti-corruption and accountability measures in Tokyo, even as he has repeated charges that donors are partly to blame for the problems because they have been more eager to spend than to comply with government procedures, transparency and Afghan customs.

The presence of so many outsiders with unlimited money have skewed the fragile Afghan economy in immeasurable ways. Foreign governments and international organizations have employed so many Afghans, usually at inflated salaries, that brain drain and unemployment are expected to soar with their departure.

“We may manage to release a few competent people back to work for their own country if they don’t all leave,” Ronald Neumann, a former U.S. ambassador to Afghanistan, said at the Brookings conference. “But overall, there’s going to be a very large economic shock to Afghanistan.”

Many Afghans are skeptical of Karzai’s renewed promises. “Like the past assistance from the world, the cash from this meeting may end up in the pockets of senior government officials,” Mohammad Nayeem Lalai Hamidzai, a member of the Afghan parliament from Kandahar, said in an interview.

Karzai set anti-corruption as his top priority when he began his second term in 2009, and just last month he called a special session of parliament to promise a government cleanup, Hamidzai recalled. With the pending troop departures, he predicted, corruption will accelerate as “people in power make sure that they can take as much as they can, because the foreigners will not be here forever.”

Since the painful public battles with the Karzai government in 2010, when members of the Afghan elite gutted the country’s largest bank, the U.S. focus on fighting corruption has waned. Asked if he has seen any real progress, a former senior U.S. official who was in the thick of those battles said, “Absolutely not.”

“We gave up our leverage” by continuing the money flow no matter how egregious the scandals, the former official said. “Every time a big issue happened, nobody wanted to push it.” Corruption was “competing with a lot of other issues out there . . . everybody saw it as something that was going to keep them from implementing policies. It always upset Karzai, and he would push back. ”

“If there’s a single lesson that comes out of this,” he said, “it’s that you can’t want it more than they want it. . . . And we wanted it worse than [Karzai] did.”

Current U.S. officials in Afghanistan acknowledge that Karzai has resisted major steps to prosecute high-level corruption or weed out the culture of bribery that is pervasive in conducting business with the government at a local level.

“If taking down organized criminal networks was easy, we would be doing it every day,” said Brig. Gen. Rick L. Waddell, who leads NATO’s anti-corruption Task Force Shafafiyat.

“When society was utterly devastated, survival meant controlling vital avenues of ingress and egress, controlling commodities and tribal trade routes,” Waddell said. “That pattern of behavior doesn’t go away.”

Along with the departure of foreign troops, Afghanistan is facing a presidential election in 2014, and “a democratically elected government . . . is non-negotiable” for international donors, the senior administration official said.

But “we have to be smart about it. We give assistance, then hold them accountable. Then give some more assistance, and hold them more accountable. . . . People obviously don’t have patience. But we’ve invested way too much in this, in money and in kids’ lives.”

Partlow reported from Kabul.