As American and coalition forces prepare to withdraw from Afghanistan by the end of 2014, the Afghan government faces a challenge as daunting as the need to take over the fight against the Taliban: assuming responsibility for an economy that has been almost exclusively dependent on outside assistance for more than a decade.

The numbers are staggering. According to the World Bank, an estimated 97 percent of Afghanistan’s roughly $15.7 billion gross domestic product comes from international military and development aid and spending in the country by foreign troops. The economy is already contracting as troops leave, and future growth will be slower, especially in urban areas and areas of conflict.

To increase the odds for a more gradual and manageable transition, the United States and other major donors pledged $16 billion in development aid through 2015 at a conference in Tokyo last week. It was an important and necessary commitment. Now they have to deliver.

The United States and other nations have promised that they will not abandon Afghanistan, which happened in 1989 after the Soviet Union was pushed out. The World Bank has warned that an abrupt aid cutoff could provoke a collapse of political authority, civil war and a greater reliance on opium profits.