WASHINGTON- The United States said Thursday that it will make "all pressures need" to free South Korean hostages held by the Taliban militants in Afghanistan.

"All pressures need to be applied to the Taliban to get them to release these hostages," Assistant Secretary of State for South and Central Asia Richard Boucher said.

He said the United States will have cooperation with Afghanistan and South Korea "to get these people released unharmed, to get them released peacefully and safely."

Boucher declined to elaborate on what pressures or efforts were being used or considered but said they included the option of military force.

Boucher made the remarks ahead of a weekend visit by Afghan President Hamid Karzai, who will meet with U.S. President George W. Bush at Camp David.

The coming U.S.-Afghan summit is expected to discuss some issues of mutual interests including the war on terror, counter narcotics and the U.S. contribution towards rebuilding of the post- Taliban Afghanistan.

Taliban militants abducted 23 South Koreans on July 19, and have shot dead two of them so far. They threatened to execute the remaining if the Afghan government fails to meet their demand which includes the release of their eight Taliban comrades.