The U.S. military is planning a major offensive in Afghanistan along the Afghan-Pakistani border this spring, Pentagon officials have confirmed to Fox News, but officials would not divulge whether it would involve moving troops into Pakistan.

According to military sources, a small number of U.S. special forces troops have already been working with Pakistani forces in the tribal sections of Pakistan, but those have been covert operations — small teams designed to hunt Taliban and Al Qaeda figures hiding in villages throughout the area.

U.S. officials have suspected that Taliban and Al Qaeda fighters travel back and forth, over the border, shifting hiding places and seeking refuge in friendly villages in Pakistan.   

Senior Defense officials still believe Usama bin Laden and top Al Qaeda leaders are in the region as well. Pakistani President Pervez Musharraf (search) has been very adamant that U.S. troops cannot cross into Pakistan and that Pakistani forces will be stepping up the hunt for terrorists along the border.

But in December 2003 there were two very sophisticated assassination attempts on Musharraf, from which he narrowly escaped.   

U.S. officials are very concerned about Musharraf's safety, and they believe those attacks were conducted by Al Qaeda operatives.

The Chicago Tribune reported Wednesday that the U.S. is planning to move the "spring offensive" into Pakistan with Musharraf's blessing. The paper cited internal Pentagon messages that purportedly say the offensive "would be driven by certain undisclosed events in Pakistan and across the region."

The paper quoted "a source familiar with the details of the plan" as saying the plan is "not a like a contingency plan for North Korea, something that sits on a shelf. This planning is like planning for Iraq. They want this plan to be executable now."

Pentagon officials would make no comment to Fox News about any possible U.S. military role in Pakistan, but they do not rule it out in the hunt for most-wanted terrorists.

U.S. officials are concerned about Pakistan's intelligence service, and many believe a large number of Inter-Services Intelligence (search) members are loyal or friendly to the Taliban and Al Qaeda.

Fox News' Bret Baier contributed to this report.