WASHINGTON, Sept 4 (Reuters) - U.S. commandos entered Pakistan this week to attack an al Qaeda target near the Afghan border in a move that could signal more intense U.S. efforts to thwart cross-border militant violence, U.S. officials said on Thursday.

The Bush administration has not officially acknowledged any involvement in the Wednesday attack on the village of Angor Adda that killed up to 20 people, including women and children, according to Pakistani officials.

Pentagon officials, speaking on condition of anonymity, said the raid by special operations forces targeted suspected al Qaeda operatives and signaled a possible intensification of American efforts to disrupt militant safe havens in Pakistan.

The United States says al Qaeda and Taliban safe havens in Pakistan are fueling an increasingly sophisticated and deadly insurgency against U.S., NATO and Afghan forces across the border in eastern Afghanistan.

Wednesday's raid has been described publicly as the first known incursion into Pakistan by U.S.-led troops since the invasion of Afghanistan in 2001.

But Pentagon officials said privately the presence of U.S. troops in Pakistan marked a return to tactics the American military has not used since soon after the Afghanistan invasion.

U.S. concerns about the growing threat of militant attacks from bases inside Pakistan prompted top U.S. military officials including Joint Chiefs of Staff Chairman Adm. Mike Mullen to meet secretly with Pakistan's military chief last week aboard a U.S. aircraft carrier in the Indian Ocean.

"The safe havens in the border regions provide launching pads for these sorts of attacks, and they need to be shut down," Mullen later told reporters at the Pentagon.

U.S. special operations forces, which lead the Pentagon's counterterrorism effort, are among 19,000 U.S. troops deployed to Afghanistan under U.S. command.

Another 14,000 U.S. forces are in Afghanistan as part of NATO's 53,000-strong International Security Assistance Force. (Reporting by David Morgan; Editing by Eric Beech)

AlertNet news is provided by