KABUL, Afghanistan – In a summer of suffering, America's military death toll in Afghanistan is rising, with back-to-back record months for U.S. losses in the grinding conflict. All signs point to more bloodshed in the months ahead, straining the already shaky international support for the war.

Six more Americans were reported killed in fighting in the south — three Thursday and three Friday — pushing the U.S. death toll for July to a record 66 and surpassing June as the deadliest month for U.S. forces in the nearly nine-year war.

U.S. officials confirmed the latest American deaths Friday but gave no further details. Five of the latest reported deaths were a result of hidden bombs — the insurgents' weapon of choice — and the sixth to an armed attack, NATO said in statements.

U.S. commanders say American casualties are mounting because more troops are fighting — and the Taliban are stiffening resistance as NATO and Afghan forces challenge the insurgents in areas they can't afford to give up without a fight.

"Recent months in Afghanistan have ... seen tough fighting and tough casualties. This was expected," the top U.S. and NATO commander, Gen. David Petraeus, said at his Senate confirmation hearing last month. "My sense is that the tough fighting will continue; indeed, it may get more intense in the next few months."

That forecast is proving grimly accurate.