WASHINGTON - US President Barack Obama and British Prime Minister David Cameron on Tuesday discussed possible options against the Libyan government, including the establishment of a no-fly zone.

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In their phone conversation, the two leaders agreed to "press forward with planning, including at NATO, on the full spectrum of possible responses, including surveillance, humanitarian assistance, enforcement of the arms embargo and a no-fly zone," the White House said.

It said the two leaders also agreed to continue working to support Egypt in its efforts to achieve a successful and peaceful transition, and reaffirmed the importance of international efforts to promote peace and stability in both Afghanistan and Pakistan.

Libya is witnessing the largest-ever unrest in the nation for the past four decades, which first broke out on February 16 in the eastern city of Benghazi. The massive protests demanding Libyan leader Muammar Gaddafi end his 42-year rule have escalated into violent clashes between anti-government protesters and pro-Gaddafi troops.