By Bate Felix and Gus Trompiz
PARIS (Reuters) - Hard-left French trade union CGT said on Friday it will call on its members to shut down operations at three of Total SA's refineries in France on Monday afternoon if a final proposal to negotiate bonuses is rejected by management.
Oil industry workers were on strike for a third day on Friday at four of France's seven refineries and unions urged employees to step up blockades to force the plants to halt production.
CGT spokesman Thierry Defresne said the union will make a final proposal to negotiate bonuses with Total's management on Saturday.
"If our proposal is rejected, we will propose to striking workers the shutdown of Grandpuits, Normandy and Feyzin petrol production units at midday on Monday," Defresne said.
He added that workers at two major oil depots extended the strike at their sites on Friday evening until Monday afternoon.
Support for continued action on Friday came after unions rejected on Thursday a 1.5 percent salary increase offer by oil industry federation UFIP, saying it was below the French inflation rate.
A spokesman for UFIP said talks to resolve the dispute had ended late on Thursday without agreement.
The CGT and fellow hard-left union FO have called on striking workers to step up blockades of refineries and fuel depots so companies are faced with supply shortages.
Defresne told Reuters earlier on Friday that Total's Grandpuits refinery south of Paris, one of the refineries where workers remain on strike, was completely blocked and had only enough crude to continue functioning until Sunday midday.
He said later on Friday that the union had allowed crude deliveries at Grandpuits and Normandy refineries to keep them running at reduced output until Monday.
But a Total spokeswoman said France's CIM oil storage and dispatch services company, which supplies crude to refineries operated by Total and Exxon Mobil Corp, was working normally.
"Total denies the fact that the Grandpuits refinery will run out of crude, forcing a shutdown," she said, although she said outbound deliveries of fuel from Grandpuits were blocked.
Some CIM employees staged a brief walkout on Thursday in solidarity with the striking refinery workers but they resumed work later in the day.
The strike over pay and bonuses adds to challenges confronting fuel companies, which are also facing protests from the "yellow vest" movement of citizens who oppose higher fuel taxes and have sporadically blockaded oil depots this week.
(Reporting by Gus Trompiz and Bate Felix in Paris; Editing by Edmund Blair and Matthew Lewis)