The attempted bombing of a U.S. commercial jetliner last Christmas highlights the growing danger of terrorists using home-made and compact explosive devices in attacks, a senior Pentagon official told Congress last week.

Garry Reid, deputy assistant defense secretary for combating terrorism, told the Senate Armed Services subcommittee on terrorism that he is most concerned about the new threat.

Reid said the Christmas Day bombing suspect Farouk Abdulmutallab, presents new worries because of the “compactness and maybe the efficiency that they are applying to this process, because it really cuts underneath our ability to detect it and do something about it.” “The tighter they compress that, the harder it gets for us,” he said.

Reid said the pockets and affiliates of Al Qaida are known and monitored but understanding what the terrorists are doing and planning is “limited” by the lack of access to ungoverned areas. The lack of intelligence means “we're still looking through a straw in many cases, so that is a concern,” he said.

Daniel Benjamin, the State Department’s counterterrorism coordinator, appeared at the same hearing to warn that there are other Islamist groups that “are looking more Al Qaida-like and seem to be interested in playing a global role in terrorism.”

Terrorists are becoming more agile and no longer need approval from senior leaders.

That danger plus the ability to sneak into the United States and use information to learn security weaknesses is a major worry.