Brazil's government could seek a third certification firm to settle differences in valuations of oil to be used in state oil company Petrobras' capitalization plan, a high-level government source told Reuters on Thursday.

This would only happen if Petrobras and Brazil's ANP energy regulator, which have each hired consultants to determine the value of the oil, were unable to agree on a price per barrel to be used in the oil-for-shares swap, the source said.

"If there is a large discrepancy in the valuation, either we bargain to reach an adequate price or we hire another certification company," said the source, who asked not to be identified. "First we have to see the prices of the certification companies.

Signs of such a discrepancy have emerged in recent days.

Petrobras and the government are treating the negotiations like a “commercial transaction,” the company said yesterday in a statement. “It’s natural that both parties would seek through negotiations to maximize their results,” the company said.

Lula received separate independent valuations on the crude reserves yesterday from Petrobras and Brazil’s oil regulator, known as the ANP, according to a joint statement from the Energy and Finance ministries and the cabinet. The government has requested more information, according to the statement.

If the price is much higher than the $5-to-$6 range, the company's minority shareholders may not participate in the stock sale.

This would leave Petrobras without the fresh capital it needs to push forward its $224 billion five-year investment program. It has ruled out further borrowing to ensure it can maintain its credit rating.