(Recasts with Marubeni comment)
SAO PAULO/TOKYO, March 12 (Reuters) - Japanese trading firm Marubeni Corp said it may back a $20 billion refinery in partnership with Brazil's state-run oil company Petrobras, but rejected a report it would foot the whole bill.
A Brazilian financial newspaper quoted Energy Minister Edison Lobao as saying Marubeni was close to bankrolling all of the $20 billion premium refinery in partnership with Petrobras.
Marubeni had agreed to look for ways to secure some funds to build the 600,000 barrel-per-day refinery but total funding was not possible, a company spokesman said.
"No letter of intent has been signed, and common sense dictates that Marubeni would not foot the whole bill in any case," said the spokesman, who refused to reveal his name, citing company policy.
Energy Minister Lobao was quoted as saying he expected construction to begin by the end of this year.
The refinery as now planned would amount to about a quarter of Brazil's current daily crude output.
Petrobras and the ministry of mines and energy did not respond to requests for comment on the minister's statements in the newspaper, Valor Economico.
"It's a firm proposal," said Lobao, adding that representatives from Japan had visited Petrobras and signed a letter of intent.
Lobao said Marubeni had agreed to take a 10 percent to 15 percent equity stake in the refinery but Marubeni said nothing had been finalised.
"So far, we've only agreed to discuss possibilities," the spokesman said.
The Japanese group would receive petroleum derivatives produced by the refinery as a form of payment from Petrobras for its share of the investment, Lobao told Valor.
Petrobras Chief Executive Jose Sergio Gabrielli told the state news agency on Wednesday that his company was committed to $174 billion in investments in the five years through 2013, though analysts have raised doubts about how it would finance such an ambitious plan.
It would mark an increase of 55 percent from the previous plan through 2012, despite most other oil majors cutting or delaying large projects amid the fragile global economic situation.
In February, Petrobras signed an agreement with the Chinese Development Bank in the hopes of securing $10 billion in financing. It also will supply 100,000 to 160,000 barrels of oil a day at market prices to China's National Petroleum Corp and Sinopec.
Petrobras is having difficulty reaching an agreement over a joint refining venture in Brazil with Venezuela's state oil company PDVSA. Petrobras has started work on the refinery despite not receiving investments or concrete commitments from PDVSA. (Reporting by Reese Ewing and Denise Luna in Rio de Janeiro and Mayumi Negishi in Tokyo; Editing by Rodney Joyce)