International donors meeting in Tokyo have pledged $16 billion in development aid for Afghanistan over the next four years.

The amount is in line with the $4 billion a year that Afghan President Hamid Karzai requested at Sunday's conference.

In his opening remarks, Mr. Karzai acknowledged that endemic corruption in Afghanistan has undermined previous aid efforts, and he promised to do more to bring that under control.

The conference is attended by representatives of about 70 countries and senior world officials, including U.N. Secretary-General Ban Ki-moon and U.S. Secretary of State Hillary Clinton. In Kabul Saturday, the top U.S. diplomat offered assurances the United States will not abandon the Afghans after American combat troops leave the country in 2014.