NAWA, Afghanistan — U.S. Marines pushed deeper into Taliban areas of southern Afghanistan on Friday, seeking to cut insurgent supply lines and win over local elders on the second day of the biggest U.S. military operation here since the American-led invasion of 2001.

On the other side of the border, U.S. missiles struck a Pakistani Taliban militant training center and communications center, killing 17 people and wounding nearly 30, Pakistani intelligence officials said.

Both U.S. operations were aimed at what President Barack Obama considers as the biggest dangers in the region: a resurgent Taliban-led insurgency allied with al-Qaida that threatens both nuclear-armed Pakistan and the U.S.-backed government in Afghanistan.

The 4,000-strong U.S. force met little resistance Friday as troops fanned out into villages in Afghanistan's southern Helmand province, although one Marine was killed and several others were wounded the day before, U.S. officials said.

Despite minimal contact, the Marines could see militants using flashlights late Thursday to signal one another about American troop movements.

Military spokesman Capt. Bill Pelletier said the goal of the Helmand operation was not simply to kill Taliban fighters but to win over the local population — a difficult task in a region where foreigners are viewed with suspicion.

Marines also hope to cut the routes used by militants to funnel weapons, ammunition and fighters from Pakistan to the Taliban, which mounted an increasingly violent insurgency since its hard-line Islamist government was toppled in 2001 by an international coalition.

The new U.S. operation will test the Obama administration's new strategy of holding territory to let the Afghan government establish a presence in rural areas where Taliban influence is strong.

As Operation Khanjar, or "Strike of the Sword," entered its second day, Marines took control of the district centers of Nawa and Garmser, and negotiated entry into Khan Neshin, the capital of Rig district, Pelletier said.

In Nawa, Marines met with about 20 Afghan men and boys, seeking to reassure them that the Americans wanted to protect them from the Taliban.

"Are you going to enter our houses?" asked Mohammad Nabi, 25, who was there with five of his younger brothers. "We are afraid that you will leave, and the Taliban will come back."

They also complained that local police were thieves not to be trusted.

Marine officers promised not to enter homes and said they would remain in the area to keep out the Taliban.

One elder with a gray beard asked the Marines whether they would prevent residents from saying Muslim prayers. The troops assured him they would not.