The top U.S. military officer says he is extremely concerned about the presence of al-Qaida safe havens in Pakistan.

Adm. Michael Mullen

During a news conference at the Pentagon Friday, U.S. Chairman of the Joint Chiefs of Staff Admiral Michael Mullen said al-Qaida militants are not only launching attacks in neighboring Afghanistan, but also inside Pakistan.

Admiral Mullen added the U.S. is mindful that Pakistan is a sovereign nation and that it is up to Pakistani President Pervez Musharraf and his military advisors to confront the problem directly.

President Musharraf has warned the U.S. against any unilateral move into Pakistan's tribal region to hunt down al-Qaida or Taliban militants. He told the Singapore newspaper The Strait Times that such move would be considered a breach of sovereignty.

In Washington, State Department spokesman Tom Casey said anything the U.S. has done or will do is in full cooperation with the Pakistani government.

Last week, the New York Times newspaper reported the Bush administration is considering expanding covert intelligence and military operations in Pakistan's tribal region, where al-Qaida leader Osama bin Laden and his deputy Ayman al-Zawahiri are believed to be hiding.

The region is also considered a base for Taliban militants planning attacks against coalition forces in Afghanistan.