Fewer foreign fighters are slipping into Afghanistan since Pakistan launched its offensive in August against Al-Qaeda and Taliban militants in border tribal regions, the Pentagon said Wednesday.

In a media briefing, US Defense Department spokesman Geoff Morrell welcomed "stepped-up operations" by the Pakistani military in Peshawar, and in Swat in particular, over the past two months.

"It is stepped up not just in terms of tempo, but in terms of effectiveness," Morrell said. "As a result, we have seen some improvement in the flow of foreign fighters across the border into Afghanistan."

He said the assessment came from US sources, but he gave no figures as to how many fewer foreign militants might be crossing the frontier since the Pakistani offensive -- launched amid strong US pressure -- began.

It appears that Pakistani operations are not only more frequent, but also "more effective," with "more forces, more resources, perhaps a better strategy" being dedicated to the mission, he said.

The Pakistan military said in late September that more than 1,000 militants -- including Al-Qaeda''s operational commander in the region, Egyptian Abu Saeed Al-Masri -- have been killed in its offensive in Bajaur.