NATO Secretary-General Anders Fogh Rasmussen said on Wednesday the alliance was not looking to intervene in Libya but its military was ready to respond to any developments at short notice.

Rasmussen said any action would require a clear United Nations mandate and widespread international support.

"NATO is not looking to intervene in Libya, but we have asked our military to conduct prudent planning for all eventualities," Rasmussen told Britain's Sky News.

"If requested and if needed we can respond at very short notice. There are a lot of sensitivities in the region as regards with what might be considered foreign military interference.

"This is why any action should be based on a very broad international support including support from the region."

British Prime Minister David Cameron struck a similar tone on Wednesday when he said that Britain was seeking international support for any measures to be taken against the Libyan leadership, including a no-fly zone.

A counter-offensive by forces loyal to Libyan leader Muammar Gaddafi has halted a rebel advance in the east and left others stranded in the western cities of Zawiyah and Misrata.

The international community has so far been hesitant about its response and U.S. Secretary of State Hillary Clinton has made it clear that Washington believes that imposing a no-fly zone is a matter for the United Nations. Rasmussen agreed.

"Let me stress the imposition of a no-fly zone would be quite a complicated undertaking and it would also require a new United Nations mandate," he said.

"The current U.N. security council resolution does not authorise the use of armed forces."