The report said that although the insurgents had less capability to directly attack American and Afghan forces, they had increasingly resorted to “assassinations, kidnappings, intimidation tactics, encouraging insider attacks and strategic messaging campaigns.”

A defense official who briefed reporters at the Pentagon sought to offer a more positive picture of the Afghan security forces’ abilities than the report would suggest. Acknowledging that the progress of the security forces had been “incremental,” the official said that many of the forces patrol and carry out some operations independently, without help from NATO. “They often don’t rely on any assistance from us at all,” said the official, who declined to be named under ground rules imposed by the Pentagon.

But the official said there were nonetheless broad problems with the Afghan National Army and the Afghan National Police, which together number 350,000 personnel. The security forces still depend over all on American air power, communications, intelligence gathering, logistics and leadership. That is true especially at the level of a brigade, which typically is composed of 3, 000 to 5,000 troops.

The official acknowledged that it would be a “challenge” to have the security forces ready to defend their own country by the end of 2014, when most American troops are to be out of Afghanistan. The White House is debating how many American forces should be left in the country after 2014 and it has opened negotiations with the Afghans on what their mission should be.

The defense official said that the rise in violence in Afghanistan — measured by what the report termed “enemy initiated attacks” — was a result of Afghan security forces pushing into Taliban-dominated areas, forcing the Taliban to fight back. The official cited three volatile districts in Kandahar Province — Maiwand, Panjwai and Zhari — as highly contested, violent areas.

Although the report did not provide month-by-month specific numbers of enemy-initiated attacks, it plotted them on a bar graph that showed, for example, that in July 2012 there were slightly more than 3,000 enemy-initiated attacks. In July 2009, before the surge began, the graph showed some 2,000 enemy-initiated attacks.

The official said it was a sign of progress that the report found that enemy-initiated attacks had declined in the city of Kandahar by 62 percent from a year ago.