KANDAGAL, Afghanistan -- US Marines and Afghan troops launched an offensive yesterday to take a remote mountain valley from insurgents tied to the deadliest blow on American forces since the Taliban regime was ousted nearly four years ago.
The operation is the biggest yet aimed at rebels believed responsible for two attacks that killed 19 US troops in June. Three Navy SEALs were killed in an ambush, and all 16 soldiers on a helicopter sent to rescue them died when it was hit by a rocket-propelled grenade.
The offensive was launched at the end of a deadly week for US forces in Afghanistan. Seven Americans have died, along with dozens of militants and civilians, reinforcing concerns that crucial legislative elections next month could be threatened by a surge in violence.
US and Afghan commanders said militants in the Korengal Valley, in eastern Kunar Province near the Pakistani border, were intent on disrupting voting. They said the valley held hundreds of Afghan rebels, as well as extremists from Pakistan, Saudi Arabia, and Chechnya.
''We want them running for their lives way up in the hills, where they can't attack polling stations," said Captain John Moshane of the Second Battalion, Third Marine Regiment, based in Hawaii. ''We want to isolate them from the community."
Hundreds of Marines and Afghan special forces troops started moving into position at one end of the valley Thursday, about 120 miles east of the capital, Kabul. They dug mortar and machine-gun pits for a resupply base in a cornfield near Kandagal, a village of about 100 farm families.
Reacting quickly, rebels fired rockets at a nearby US post and a troop convoy but did not hit anything.
US and Afghan forces hiked into the rugged mountains Friday and yesterday, many leading lines of donkeys laden with food and water. A-10 attack planes circled high above.
The operation was expected to last at least two weeks, Moshane said.
One main objective is breaking up a network of militants led by a local Taliban officer, Ahmad Shah, also known as Ismail, who claimed responsibility for the June 28 attacks, said Kirimat Tanhah, a commander in the US trained and financed Afghan special forces.
Shah is suspected of having ties to Al Qaeda militants in Pakistan, he said.
''Ismail's men ambushed the SEAL team and shot down the helicopter," Tanhah said. ''Many of them are foreigners and have trained in Pakistan and elsewhere."
He said Shah also pays impoverished villagers to fight for him.
Lieutenant Colonel Jim Donnellan, commander of the Marine battalion, said the valley was a base for lots of other ''bad guys" besides Shah, including Al Qaeda militants.