SCOTT SIMON, host:
Even before the U.N. Security Council authorized military action against Moammar Gadhafi, counter-terrorism officials in the United States were looking at what would happen if the Libyan leader got even more desperate and decided to resort to terrorism.
Libya was behind the 1998 downing of Pan-Am Flight 103 over Lockerbie, Scotland. It was considered a sponsor of terrorism until Gadhafi renounced it a few years ago.
NPR's Dina Temple Raston reports on the administration's concern about the terrorism threat Gadhafi presents now.
DINA TEMPLE-RASTON: Libya and terrorism hit close to home for President Obama's top terrorism adviser. His name is John Brennan, and he had a friend on Pan Am Flight 103. That's the plane that went down over Lockerbie, Scotland.
And while it's unclear if Gadhafi personally ordered the attack, it has since come out that Libya was behind the bombing.
Mr. JOHN BRENNAN (Deputy National Security Adviser for Homeland Security and Counterterrorism): Gadhafi has the penchant to do things of a very - a concerning nature.
TEMPLE-RASTON: That's Brennan during an interview yesterday.
Mr. BRENNAN: We have to anticipate and be prepared for things that he might try to do to flout the will of the international community. Terrorism is certainly a tool that a lot of individuals will opt for when they lose other options.
TEMPLE-RASTON: And with the U.N. threatening military action against the Libyan leader, his options are dwindling.
Among the U.S.'s major concerns: Gadhafi is thought to have stores of mustard gas. U.S. intelligence officials tell NPR that they have a pretty good idea where those stockpiles are.
Mr. BRENNAN: And its clearly something that were focused on. There are a number of things within Libya that we're concerned about, and we're trying to make sure that we're able to identify that which we need to address - and Ill leave it at that.
TEMPLE-RASTON: Libya is near the top of a long list of countries that have U.S. counter-terrorism officials concerned. The general turbulence in the Middle East and North Africa has provided political vacuums al-Qaida can exploit. And the U.S. is now having to work, in many cases, with new partners - political leaders who don't necessarily subscribe to counter-terrorism agreements the U.S. has made in the past.
For example, on Thursday, Egypt released a man who had been in prison in Cairo for the past 11 years. Hes the brother of al-Qaeda's second in command, Ayman al-Zawahri. Brennan said those kinds of events worry U.S. officials. There can't be a revolving door, he said, for terrorists in these countries.
Dina Temple-Raston, NPR News, New York.