WASHINGTON - The second-ranking U.S. commander in Afghanistan says Afghan security forces suffered more battle casualties this year than last year and have reached a level that cannot be sustained in a successful fight against the Taliban.

Lt. Gen. Joseph Anderson told reporters at the Pentagon by video from his headquarters in Kabul that the number of Afghans killed in battle rose from 4,350 last year to 4,634 so far this year.

The toll increased even though the number of attacks by Taliban fighters has decreased to about 18,000 this year from about 24,000 last year. Afghan government forces, on the other hand, have initiated more attacks on the Taliban this year.

Anderson said Afghans must improve the quality of medical care for wounded troops, starting at the point of injury.