The Pentagon on Friday painted a guardedly optimistic picture of the war in Afghanistan, saying that U.S. and allied forces had made “tangible progress” against the Taliban over the past six months and that conditions were right to withdraw at least some U.S. troops this summer.

In a report to Congress assessing the war effort through the end of March, the Defense Department presented its most positive view of the Afghanistan war in years. Although the Pentagon offered plenty of caveats and studiously avoided using words such as “victory” or “winning,” it largely concluded that the Obama administration’s strategy was working.

“The situation on the ground is fundamentally changing,” said a senior defense official, who spoke to reporters on the condition of anonymity under rules fixed by the Pentagon.

The Taliban announced Saturday that they will begin their spring offensive against the U.S.-led coalition on Sunday. Targets will include military bases and convoys as well as Afghan officials, the Taliban said in a statement.

In tone and substance, the Pentagon report was rosier than a similar assessment presented to Congress by the White House this month. In its report, the White House noted that the Taliban had gained strength in the Afghanistan-Pakistan border region and that there was “no clear path” toward defeating insurgents who hide out in Pakistan, beyond the reach of U.S. and NATO troops.

The Pentagon, in contrast, made only brief references to Taliban havens in Pakistan, saying that more effort is needed “to eliminate these sanctuaries.”

The report’s inattention to Pakistan’s role in the Afghanistan war was striking given recent complaints by senior U.S. military officials. On April 20, during a visit to the Pakistani capital, Islamabad, Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, bluntly accused Pakistan’s intelligence agency of providing support to the Haqqani network, a Taliban affiliate that leads the insurgency in eastern Afghanistan.

The Pentagon and White House are each required to evaluate the war’s progress in regular reports to Congress. In general, both have said that President Obama’s strategy has borne fruit since he announced in December 2009 that he would deploy 30,000 extra troops to Afghanistan.

There are about 100,000 U.S. troops in Afghanistan today, but Obama has promised to withdraw at least some of them starting in July. Gen. David H. Petraeus, the commander of U.S. and NATO forces in Afghanistan, is scheduled in the coming days to make specific recommendations on the scope of the withdrawals.

Plans for a partial pullout come as domestic support for the war plummets. A Washington Post-ABC News poll in March found that two-thirds of Americans feel the decade-long war is no longer worth fighting, the highest proportion yet.

The Pentagon report focused on its efforts to bolster the size and ability of Afghanistan’s security forces so they can eventually take over responsibility for fighting the Taliban. Defense officials cited a litany of challenges that continue to dog the Afghan forces — illiteracy, high dropout rates, a lack of trainers — but said things were improving in general.

In particular, the Pentagon said new local Afghan police and village security forces have proved effective in deterring the Taliban. In December, Petraeus announced plans to triple the size of the local Afghan police forces — which one U.S. military official described as “community watch on steroids” — to 30,000.

According to the Pentagon, the Taliban sees the local police forces as “significant threats, as they empower the local populace to reject the insurgency and connect them to the government.” The report said that the Taliban has targeted the local forces with assassinations and kidnappings but that the attacks were “largely ineffective.”