BERLIN — The major donors and Afghan government officials meeting in Tokyo on Sunday to discuss future aid to Afghanistan have to face up to a bitter truth: As much as $1 billion of the $8 billion donated in the past eight years has been lost to corruption. All governments in Tokyo must show that business as usual cannot continue. An agreement worth $4 billion is at stake.

Turning off the aid taps is not an option. This would hurt the poorest, increase instability and likely lead to illicit flows taking the place of donor funding. Donors and the Afghan government need an enforceable plan to tackle the issue. They don’t need more words.

Corruption in the country is nothing new, but it is worsening. Afghanistan has had a long history of conflict, contraband and war. It falls almost at the bottom of the list of the most corrupt and poorly governed countries, including the Corruption Perceptions Index produced by Transparency International.

Estimates from local watchdog Integrity Watch Afghanistan show bribe payments — for everything from enrolling in elementary school to getting a permit — doubled between 2007 and 2009, topping $1 billion a year. Corruption and black-market trading, which is closely linked to drugs and arms trafficking, have reached over $12 billion annually, according to calculations by NATO.