Lebanon has called for US mediation after a vessel appeared to start producing gas for Israel in waters disputed by Beirut. According to Lebanon, such a move would be tantamount to aggression, AFP reported.

The vessel, operated by London-based Energean Plc, arrived at the Karish gas field, part of which is claimed by Lebanon, on Sunday.

The move immediately drew condemnation from the Lebanese president and prime minister, who held talks on Monday to discuss next steps.

They agreed to invite U.S. Ambassador Amos Hochstein to Beirut to consider resuming negotiations to demarcate Lebanon's southern maritime boundary, which Prime Minister Najib Mikati said stalled last May.

Any exploration, drilling or mining conducted by Israel in the disputed areas constitutes a provocation and an act of aggression, the statement said.

Israel and Lebanon resumed maritime border talks in 2020, but the process was halted after Beirut said the map used by the United Nations in the talks needed to be changed.

Lebanese officials themselves are divided over the demarcation line, and the state's official position appears inconsistent.

The demarcation line, known as Line 29, would give Lebanon more territory further south, including parts of the Karish gas field.

On Sunday, Lebanese officials said any Israeli action in disputed waters would constitute a hostile act and an attack on Lebanon's natural resources.

But for Israel, Karish is within Israel's UN-recognised exclusive economic zone and not in disputed territory, a senior Israeli official told AFP on condition of anonymity.

Energean, which will operate Karish, said the first gas flows from the field should come in the third quarter of 2022.