WASHINGTON -  The United States and its allies have made "tangible progress" in the Afghanistan war, providing the needed momentum to transfer control of seven regions to Afghan forces this summer, according to a Pentagon report that gives the first assessment since the infusion of 30,000 more American troops to the battlefield late last fall.

Sounding a more optimistic tone than previous reviews, the semiannual report to Congress also describes difficult challenges ahead, including a significant lack of military trainers and border patrols and the slow political and governance development that could threaten the progress made in the last six months.

It comes on the same day that senior NATO officers revealed that they have picked up intelligence suggesting that Afghan insurgents are planning a spate of violent attacks across the nation in the next several days. They said the militants want to demonstrate they remain a powerful force despite setbacks they suffered under heavy pressure from tens of thousands of Afghan and NATO troops during the past year.

A senior defence official told reporters at the Pentagon Friday that the latest review takes a broader, long-term look at the progress in Afghanistan. The official also agreed there still will be significant attacks as insurgents return for the spring fighting season.

The official, who spoke on condition of anonymity because he was not authorized to talk publicly, said estimates suggest the violence in Afghanistan could peak in the next 12 months as the Taliban tries to regain lost ground and let Afghans know they will be back.

Unlike previous reports, the latest Pentagon review does not detail by district the progress of the Afghan government's effort to win the trust of its people.

A year ago, Pentagon leaders said that of 121 major regions of Afghanistan examined by the NATO-led international force, 73 were considered sympathetic or neutral to the Afghan government. The April 2010 report found that there were no districts where the Afghan government held full control and was completely supported by the local population.

Against this backdrop, Gen. David Petraeus, the top U.S. commander in Afghanistan, soon will deliver options to Defence Secretary Robert Gates for the size and pace of the withdrawal of American troops that is expected to begin in July. There has been continuing debate between the administration and the military over how big the drawdown will be, with some estimates ranging from a few thousand to several thousand.

There are roughly 100,000 U.S. troops in Afghanistan.

In an Associated Press interview this month, President Barack Obama said the withdrawal will be significant and not "just a token gesture." A key to the troop cuts, however, will be the status of the fragile improvements in security in once-lawless areas of Afghanistan and how quickly the Afghans can take charge in the first regions slated for handover.

President Hamid Karzai has said the first phase of transition to his forces will start in July, and the seven areas will include the provincial capitals of Lashkar Gah in southern Afghanistan, Herat in the west, Mazer-e-Sharif in the north and Mehterlam in the east.

The report released Friday echoes predictions from senior military commanders that there will be a tough fighting in the warm months ahead, and it shows spikes in violence in the east and southwest regions where troops have been engaged in fierce battles with insurgents.

"The months ahead will see setbacks as well as successes," the report said. "There will be difficult fighting and tough losses as the enemy tries to regain momentum and key areas lost in the past six months."

Commanders have attributed the increase to the higher number of U.S. and coalition forces going after enemy strongholds, as well as the mild winter.

At the same time, however, the report said the momentum of the insurgents has been "broadly arrested" and their morale has begun to erode. Hundreds of insurgent leaders have been killed or captured, it said, and since last July 700 former Taliban have been officially reintegrated into Afghan society and another 2,000 insurgents are in various stages of the process.

Pressure from NATO combat operations over the winter had its greatest effect on the lower and middle levels of the insurgency, the report said, making it increasingly difficult for their senior leaders to keep their subordinates committed to the fight.

"The majority of fighters and sub-commanders, operating in or near their home districts and villages, have reportedly felt removed from senior insurgent leaders who are perceived as living in relative safety outside the major conflict areas and who are benefiting financially from the fighting," the report said.

While this disconnect should not be overstated, it does suggest that "seams within the insurgency may be widening," it said.