U.S. Marine spokesman Major WIlliam Pelletier says the goal was to disrupt the Taliban presence and supply chain.
U.S. Marines pressed deeper into a key Taliban stronghold in southern Afghanistan Saturday, in an offensive aimed at disrupting the militants' supply line.
The operation, known as Cobra's Anger, was launched Friday in the Now Zad valley of Helmand province.
It is the first major U.S.-led offensive since U.S. President Barack Obama announced the new U.S. strategy for the war.
The operation involves about 1,000 U.S. Marines, 150 Afghan troops and an unspecified number of British soldiers.
Officials say the advancing forces killed at least four Taliban militants in the operation's first day and seized hundreds of weapons and explosives.
No casualties have been reported among the troops.
Now Zad was once the second biggest town in Helmand, but is now nearly empty, after residents fled ongoing violence. Taliban forces now use the area to transport drugs, weapons and fighters.
The head of the U.S. Central Command, General David Petraeus, told the Associated Press the offensive lays the groundwork for the arrival of some 30,000 additional U.S. troops, many of whom will be deployed in the south.
General Petraeus says the military has been working for months to extend security around key towns in southern Afghanistan, where the Taliban influence is strong.
President Obama announced the additional U.S. forces this week, saying they will help accelerate the transfer of security responsibility to Afghan forces and allow U.S. forces to begin leaving the country by July 2011.
Helmand province produces the largest share of Afghanistan's opium crop, which supplies 90 percent of the world's heroin.
The illicit drug trade provides a key source of revenue for Taliban insurgents.
Some information for this report was provided by AFP, AP and Reuters.