The Pentagon said today that Libya's stockpile of chemical weapons are "secure" but that an arsenal of thousands of shoulder-launched missiles remained cause for concern.

Asked if sites containing chemical weapons, including over 10 tons of mustard gas, were safe, spokesman Colonel Dave Lapan said: "Yes."

But he declined to offer more details, only saying that "clearly those are dangerous agents and weapons ... we continue to monitor that."

There were no plans to send US troops in to secure the chemical weapons sites, he told reporters.

Although Muammar Gaddafi's regime retained the mustard gas, it lacked the military means to launch an attack with the chemical, according to arms control experts.

Gaddafi joined the Organisation for the Prohibition of Chemical Weapons in 2004 after renouncing weapons of mass destruction in December 2003, but still had to eliminate 11.25 tons of mustard gas when the uprising to remove him from power began in February.

All 3,563 munitions -- such as bombs, shells and missiles -- that could serve as a carrier to distribute mustard gas have been destroyed, according to the OPCW.

Lapan said the United States was also concerned about a plethora of conventional arms and ammunition, including shoulder-launched surface-to-air missiles.

The shoulder-launched missiles in particular posed a potential danger, he said.

"They remain a concern, because of their portability."