Despite improvements to security in Afghanistan, militants operating from safe havens in Pakistan and chronic problems with the Kabul government pose significant risks to a "durable, stable Afghanistan," according to a Pentagon progress report released Friday.

More than a decade since the Sept. 11 terror attacks and the start of the Afghan war, the U.S. and its allies have reversed violent trends in much of the country and the transition to Afghans taking charge of security has begun in seven key areas, including major cities such as Kabul and Herat.

"Security gains during (the past six months) have provided a firm foundation for the transition of security responsibilities to the Afghan government" and its security forces, the report said.

However, cross-border attacks have increased in recent months due to insurgents' safe havens in Pakistan and the support they received from within its borders.

"The insurgency remains resilient and, enabled by Pakistani safe havens, continues to contest" Afghan security forces throughout the country, especially in the east, according to the semi-annual report sent to Congress.

The report also identified chronic problems with the Afghan government, including widespread corruption, delays in reforms and political disputes, as obstacles to U.S. and coalition efforts to get Kabul to take over security for the country.

The Unites States has some 100,000 troops in Afghanistan and plans to bring most forces home by the end of 2014. President Barack Obama announced this past summer that 10,000 troops will be redeployed by the end of the year. The 33,000 troops that Obama sent as a surge force will be out by the end of September 2012, leaving about 68,000 troops.

"Transition remains on track with no demonstrated effort by the insurgency to target the process," the report said.

Overall, the report gives a more upbeat assessment of the military strategy and its future prospects. For the first time in several years, the report does not describe the progress in Afghanistan as "fragile and reversible" _ an omission that a senior defense official said Friday was deliberate.

Instead, the report focused on the continuing risk areas, such as the safe havens in Pakistan and weak governing in Kabul.

The defense official, who spoke on condition of anonymity because they were not allowed to speak publically on the issue, said that U.S. and coalition forces will be turning more attention to the eastern border region. But the official could provide no details on what that would look like, or if it will mean a substantial shift in U.S. troops to the embattled region.

The latest progress report _ the last one was in April _ strikes a more critical tone than previous Pentagon reports about Pakistan's failure to crack down on safe havens for militants along the border with Afghanistan, arguing that these havens enable insurgents considered the greatest threat to American troops.

The report said the relationship between Afghanistan and Pakistan had improved early on, but several events severely strained those ties. Most notably was the May 2 U.S. raid deep inside Pakistan that led to the death of al-Qaida leader Osama bin Laden.

Cross-border attacks diminished in August, but high-profile attacks in September, including the assault on the U.S. embassy in Kabul, were a significant setback.

The report said these attacks "were carried out by the Haqqani network and directly enabled by Pakistani safe haven and support."

U.S. Army Lt. Gen. Curtis Scaparrotti, who directs day-to-day military operations in Afghanistan, told reporters on Thursday that the attacks are about four times more frequent than they had been in the past year.

The United States in recent weeks has stepped up criticism of Pakistan and its counterterrorism cooperation but has at the same time sought to cajole the increasingly angry and resistant Pakistanis into doing more. As tensions rose between Washington and Islamabad, Secretary of State Hillary Rodham Clinton delivered an unusually blunt warning to the Pakistanis, saying during a visit to Kabul last week that they "must be part of the solution" to the Afghan conflict.

Clinton said the Obama administration expects the Pakistani government, military and intelligence services to "take the lead" in not only fighting insurgents based in Pakistan but also in encouraging Afghan militants to reconcile with Afghan society. She said the U.S. would go it alone if Pakistan chose not to heed the call.

After leaving Kabul, Clinton made the same points to Pakistani officials in Islamabad, where she led a high-level U.S. team, including CIA director David Petraeus, seeking to repair badly strained ties. Those meetings appear to have dulled the intensity of Pakistan's anger but there has not yet been any clear sign that the crisis is over.

Last month, then-Joint Chiefs of Staff Chairman Adm. Mike Mullen said the Haqqani network, which is affiliated with the Taliban and al-Qaida, "acts as a veritable arm" of Pakistan's intelligence agency. Mullen accused the network of staging an attack against the U.S. Embassy and NATO headquarters in Kabul on Sept. 13 as well as a truck bombing that wounded 77 American soldiers. He claimed Pakistan's spy agency helped the group.

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Associated Press reporters Matthew Lee and Lolita C. Baldor contributed to this story.