ARLINGTON, Va. — Despite the addition of more than 50,000 U.S. troops to Afghanistan over the past year, there still aren’t enough forces to conduct operations in the majority of key areas, according to a congressionally mandated report released Wednesday on progress in Afghanistan.

Coalition forces have decided to focus their efforts on 121 key districts in Afghanistan, but right now, NATO has enough forces to operate in only 48 of those districts, the report said.

There are currently 86,000 U.S. troops in Afghanistan, up from about 30,000 when President Barack Obama took office. By August, there will be 98,000 U.S. troops in Afghanistan.

With the rest of the U.S. and foreign partner troops that will arrive in Afghanistan this year, coalition and Afghan security forces will be able to focus on all 121 districts "over coming months," a senior Defense official said Wednesday, declining to be more specific.

The 150-page progress report said that Afghanistan’s deteriorating situation has leveled off, but violence still increased 87 percent between February 2009 and March 2010. A senior Defense official attributed the increase to the presence of more troops in Afghanistan moving into tougher areas.

The most significant challenge that coalition forces face is fielding enough high-quality Afghan troops and police to assume primary responsibility for security in Afghanistan, the official said. The need for police trainers is particularly pressing.

While the Afghan police force has grown substantially over the past year, many were rushed into service for the August presidential elections with little or no training, the report said. Those police will complete their retraining by July.

Meanwhile, corruption is a continuing problem, according to the report, the fifth in a series required every 180 days.

While the Afghan government has taken steps to fight corruption, "real change remains elusive and political will, in particular, remains doubtful."

"The government of Afghanistan, as a whole, has yet to exercise sustained leadership on this critical issue or to take the initiative, instead of merely responding to international community initiatives, pressure, and encouragement," the report said.

Frustration with the government is one reason behind the success of the insurgency.

Insurgents in Afghanistan regard 2009 as their "most successful year," according to the progress report.

While instability has leveled off, the insurgency has a "robust means of sustaining its operations."

"A ready supply of recruits is drawn from the frustrated population, where insurgents exploit poverty, tribal friction and lack of governance to grow their ranks," the report said.

Among the insurgents’ strengths is their ability to carry out media campaigns, conduct complex attacks, and crate a "shadow government" that undermines the Afghan government’s legitimacy.

But the insurgency does have weaknesses:

• Fissures among local insurgent leaders
• Violence against civilians
• Over-reliance on outside support
• Layered command structure that makes it hard to act on a decentralized level
• Dependence on marginalized or threatened segments of the Pashtun population.

The report anticipates a "significant insurgent response" to NATO operations in Kandahar, expected to kick off in June.

While NATO troops have cleared some insurgent strongholds, the Afghan government has been slow establishing a presence there.