The Norwegian Oil and Gas Association, which negotiated on behalf of energy firms, confirmed the agreement.

Operator Equinor had said a strike could reduce Mongstad's storage and harbour capacity and disrupt production at fields responsible for a third of the country's crude output and more than 40% of natural gas exports.

Norway, western Europe's largest oil and gas producer, pumps about 2.1 million barrels per day (bpd) of crude, while gas production amounts to 2 million barrels of oil equivalent per day (boed).

State-controlled Equinor on Friday said a strike could disrupt production at the major Johan Sverdrup and Troll fields, as well from five smaller fields, namely Kvitebjoern, Visund, Byrding, Fram and Valemon.

The fields produced 680,000 bpd of crude and had a gas output corresponding to about 850,000 boed in November, according to data from the Norwegian Petroleum Directorate (NPD).

Although only a dozen workers would have gone on strike initially, they are key to loading vessels and handling the ships' arrivals and departures at the busy Mongstad terminal.

In case of a protracted conflict, a strike could also have spread to other onshore facilities, with as many as 800 oil and gas workers potentially involved, Safe had warned.

(Editing by Gwladys Fouche)

By Terje Solsvik