(Adds union comment paragraph 3, Petrobras comment para 5, details and comment on talks paragraph 4, 6-9, Petrobras background paragraphs 10, 11)
RIO DE JANEIRO, Sept 3 (Reuters) - Brazil's main oil workers union federation FUP said on Thursday it has delayed a planned open-ended strike at state-run oil company Petroleo Brasileiro SA until Sunday at the earliest.
Previously the union notified Petrobras, as the oil company is known, that a strike could start as early as 0:00 Friday morning (0300 GMT), the press office said. It delivered the new notification on Thursday.
"This is part of our strategy," said Alessandra Muteira, FUP's press spokeswoman. "We won't provide details except to say we are now on a strike footing. A strike could happen at any time starting Sunday."
The change came after FUP representatives walked out of a bargaining session with Petrobras officials earlier on Thursday.
Petrobras in a statement said it met with the union on Thursday and that it presented its new negotiating model and that it planned to present a contract proposal to the union on Sept 10.
FUP is pressuring Petrobras to scrap plans to sell $15.1 billion of assets by the end of 2016, including a stake in the company's fuels-distribution unit Petrobras Distribuidora SA.
Union negotiators left the talks after Petrobras told FUP that its main subsidiaries would each conduct separate contract talks with union representatives, FUP said in a statement.
The union wants a single contract with Petrobras and is opposed to separate talks with Petrobras pipeline and tanker shipping unit Transpetro, Petrobras Distribuidora and other subsidiaries.
"FUP considers this an affront to the union and reaffirms that the priority of the oil workers at this moment is to discuss the Agenda for Brazil," the statement said without mentioning any salary or benefit demands.
The union's agenda includes blocking a proposal to change Brazil's oil law that would free Petrobras from an obligation to hold a minimum 30 percent stake in all new developments and run any consortium in an oil-rich offshore area known as the Subsalt Polygon.
The Subsalt Polygon is a region off the coast of Rio de Janeiro where Brazil already gets about 90 percent of its oil. It's also where large new oil and gas resources have been found trapped by a layer of mineral salts deep beneath the seabed.
A massive corruption scandal, a plunge in oil prices and a $130-billion debt, the largest of any oil company, have forced Petrobras to cut its investment plan by 40 percent over five years and acknowledge it cannot take on new subsalt projects. (Reporting by Jeb Blount; Editing by Chris Reese and Andrew Hay)