US Secretary of State Mike Pompeo on Friday pressed Libya's Turkish-backed government for a ceasefire and criticized the flow of weapons as Tripoli pushes back against a year-old rebel offensive.

Pompeo placed a phone call to Prime Minister Fayez al-Sarraj to "reiterate US opposition to the continued level of weapons and munitions being brought into the country," the State Department said.

Pompeo and Sarraj "emphasized the importance of an immediate halt to the fighting and return to political dialogue," a statement said.

Pompeo's statement did not name any country for sending in weapons, but the Government of National Accord's key military supplier is Turkey, which signed a pact with Tripoli in November.

A report last month by the International Crisis Group said that Turkey has sent into Libya at least 100 military officers, shiploads of weapons and aerial defenses as well as at least 2,000 pro-Turkish fighters from Syria.

The United States officially backs the UN-recognized government and opposes Haftar's offensive.