US progress in the war in Afghanistan is "uneven", with only a modest improvement over the last few months and an increase in violence, according to a Pentagon report published yesterday.

The report, a six-monthly assessment sent to Congress, says that while there has been a slight improvement in security, the number of Afghans recording their security situation as "bad" is at its highest since 2008.

The modest improvements come in spite of an increase in the number of US forces in Afghanistan over the year.

The assessment offers a taste of a bigger report to the White House planned for early next month, a review of progress demanded by Barack Obama.

The president, depending on whether security improves, hopes to begin reducing the number of US troops in Afghanistan next July, with the bulk out by the end of 2014.

The speed at which US forces withdraw is largely dependent on the assessment of progress, according to the White House.

Obama has been criticised for setting deadlines for troop withdrawals, and the Pentagon obliquely refers to that.

"The Taliban's strength lies in the Afghan population's perception that coalition forces will soon leave, giving credence to the belief that a Taliban victory is inevitable," the report says.

Since taking office in January last year, Obama has increased the number of US troops in Afghanistan to about 100,000. The report said: "The deliberate application of our strategy is beginning to have cumulative effects, and security is slowly beginning to expand."

But it added: "Progress across the country remains uneven, with modest gains in security, governance, and development in operational priority areas."

The Taliban are maintaining momentum in some areas, while in others the balance is shifting towards Nato and Afghan forces. Combat incidents have increased 300% since 2007. Afghan forces are being trained faster than scheduled, but retention levels are poor, the report said.

Only marginal improvements in security have been made in Helmand and Kandahar, where the Taliban have a strong presence.

"While kinetic activity is at a historic high, we are seeing some early indications that comprehensive Coin (counter-insurgency) operations are having localised effects in portions of Helmand and Kandahar provinces," says the report.

The report said that while there had been "increased pressure on insurgent networks over the past several months, the insurgency has proven resilient with sustained logistics capacity and command and control".

The Taliban attempts to cut off access to safe havens and supply links, mainly in Pakistan but also in Iran, "have not produced measurable results".

The report covered the period April to September and Pentagon officials argued that it does not take account of progress made over the last month and a half, particularly round Kandahar.