France on Tuesday urged caution over supplying arms to Libya's fledgling unity government, saying an EU naval operation should ensure that weapons do not fall into the wrong hands.

"As was decided... in Vienna, it is essential to help the national unity government to control and ensure the security of Libyan territory," the French foreign ministry said in an online press briefing.

But it stressed that only the UN-backed government of Prime Minister Fayez al-Sarraj "can legitimately request exemptions to the arms embargo," the foreign ministry said.

"The arms embargo must be maintained. France would like the mandate of (EU Operation Sophia against people smuggling) to be broadened to cover this."

The United States, Italy and Libya's friends and neighbours agreed at a meeting in Vienna on Monday to arm the war-torn country's fledgling unity government to fight the Islamic State threat.

France and Britain are preparing a draft resolution at the United Nations to allow EU ships in the Mediterranean to intercept vessels suspected of carrying weapons to Libya, diplomats said Monday.

The UN arms embargo was imposed on the north African country in 2011, during the uprising against Moamer Kadhafi.

The UN resolution would also call for the naval force codenamed Operation Sophia to train the Libyan coastguard.