U.S. forces have encountered little resistance in the initial phase of a massive operation by some 4,000 Marines in Taliban-controlled areas of southern Afghanistan, but that''s a common tactic by insurgents.

The hard part will be winning support in a region where few foreigners have ventured. The lack of resistance by insurgents in Helmand province in the mission''s first phase could change in coming days, said Capt. Bill Pelletier, a spokesman for the unit, on Friday.

The operation''s focus is not killing the Taliban but winning the local population over, Pelletier said — a difficult task in a region where foreigners are viewed with suspicion, and few have stayed for long.

"We are not worried about the Taliban, we are not focused on them. We are focused on the people," Pelletier said. "It is important to engage with the key leaders, hear what they need most and what are their priorities."

The offensive along 55 miles (88 kilometers) of Taliban-controlled areas in southern Afghanistan will test the Obama administration''s new strategy of holding territory to let the Afghan government sink roots in Helmand.