KABUL, Afghanistan -- More U.S. military deaths in the past 10 months of the Afghan war than in the first five years of the conflict. More boots on the ground than in Iraq.

As the U.S. military death toll in the Afghan conflict reached the 1,000 mark, a fight that has become "Obama's war" now faces its greatest challenge, a high-risk campaign to win over a hostile population in the Taliban's southern heartland.

More casualties are expected when the campaign kicks into high gear this summer. The results may determine the outcome of a nearly nine-year conflict that has become the focus of America's fight against Islamist militancy.

The 1,000th U.S. military death occurred in a roadside bombing Friday, just before the Memorial Day weekend when America honors the dead in all its wars.

A NATO statement did not identify or give the nationality of the victim. U.S. spokesman Col. Wayne Shanks said the trooper was American, the 32nd U.S. war death this month by an Associated Press count.

The grim milestone reflects the acceleration in fighting since President Barack Obama shifted the focus from Iraq to Afghanistan, where al-Qaida plotted the Sept. 11, 2001, terror attacks in the United States.

Obama's decision brought a heavy price.

In the past 10 months, at least 313 U.S. service members have been killed in the war, more than the 295 who died in the first five years of the conflict.

The number of U.S. troops in Afghanistan now has surpassed the total in Iraq -- roughly 94,000 in Afghanistan compared with 92,000 in Iraq. In 2008, the U.S. force in Afghanistan numbered about 30,000.

For many of the U.S. service members in Afghanistan, the 1,000-mark passed without fanfare.

Capt. Nick Ziemba of Wilbraham, Mass., serving with the 1st Battalion, 17th Infantry Regiment in southern Afghanistan, said 1,000 was an arbitrary number and would have no impact on troop morale or operations.

"We're going to continue to work," he said.

As casualties rise, the slide in overall support for the war may accelerate.

A majority of Americans, 52 percent, say the war is not worth the cost. The negative assessment in a new Washington Post-ABC News poll followed a brief rise in support for the war after Obama refocused the U.S. war plan last year.

Those figures could change dramatically depending on the outcome of the coming operation in Kandahar, the biggest city in the south, with about a half million people, and the Taliban's former spiritual headquarters.

U.S. commanders think Kandahar is the key to the ethnic Pashtun south, the main theater in the war.

Winning over the southern population won't be easy. Many Pashtuns, who form the overwhelming majority of the Taliban, view the central government as corrupt and ineffectual, dominated by rival communities of ethnic Tajiks, Hazaras and Uzbeks.

Many Pashtuns prefer negotiations with the Taliban, even if talks end with a significant political role for the movement.

"The Taliban are not outsiders. They are our own people," said Kandahar farmer Raaz Mohammad. "They should sit and resolve the situation. This is the only thing they can do if they want peace over here."