The international coalition force is planning a ground operation in Libya that could start in late April, a high-ranking Russian intelligence service source said on Friday.
"Information coming via different channels shows that NATO countries, with the active participation of Britain and the United States, are developing a plan for a ground operation on Libyan territory," he said.
"From all indications, a ground operation will be launched if the alliance fails to force the Gaddafi regime to capitulate with air strikes and missile attacks."
If the events in Libya follow this scenario, the ground operation could start "in late April-early May," he added.
The UN Security Council imposed a no-fly zone over Libya on March 17, allowing "all necessary measures" to protect civilians from Muammar Gaddafi's attacks on rebel-held towns.
The operation to enforce the no-fly zone, codenamed Odyssey Dawn, is being conducted jointly by 13 states, including the United States, Britain and France.
Western warplanes have flown more than 300 sorties over the North African country and fired 162 Tomahawk missiles in the UN mission.