UPDATE 2-Brazil seeks high crude price in oil swap-report

* ANP sees $5-$6/bbl as "too low" for oil-for-share swap

* Could seek price as high as $8/bbl, Estado reports

* State could boost stake in Petrobras to 40 pct (Adds details in paragraph 3, context, analyst quote, share prices in paragraphs 8-11)

By Brian Ellsworth and Denise Luna

RIO DE JANEIRO, Aug 10 (Reuters) - Brazil's government should charge state-controlled oil company Petrobras the highest possible price per barrel for crude reserves to be used in an oil-for-shares plan, a top energy official said in an interview published on Tuesday.

The price per barrel is crucial for investors eyeing the transaction because markets are concerned the government may charge Petrobras (PETR4.SA)(PBR.N) too much for the oil to be used in the swap, leaving Petrobras overpaying for the asset and possibly diluting shares.

Analysts see the transaction becoming politicized in the run-up to the October presidential vote as nationalist sentiment pushes some government officials to seek a higher price per barrel in the swap, which could weaken the company's capacity to finance its massive offshore oil crusade.

Haroldo Lima, head of the National Petroleum Agency (ANP), speaking in an interview in the Folha de S. Paulo newspaper, said $5 to $6 per barrel is "too low." The O Estado de S. Paulo newspaper, citing sources, said the state should seek a price closer to $8 per barrel.

"That price (between $5 and $6 a barrel) is just too low, but that's my personal opinion," Lima told Folha.

Uncertainty over the transaction, and particularly the price per barrel to be used, has weighed on Petrobras shares since the plan was introduced last year, leaving the company's stock vastly underperforming the broader Brazilian stock index.

The capitalization is the cornerstone of Brazil's campaign to tap billions of barrels in deep water, a move President Luiz Inacio Lula da Silva sees as crucial to pushing the country toward developed-nation status.

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Brazil oil graphic: link.reuters.com/wec82j

Petrobras output graphic: link.reuters.com/daj42j

Details on capital plan: [ID:nN12225996]

Graphic of shareholders: link.reuters.com/quf29k

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If the price per barrel is much higher than the $5-$6 range the market sees as fair, the company's minority shareholders may not participate in the sale.

This would leave Petrobras without the capital injection it needs to move forward with its plan to tap oil reserves in the subsalt region, a vast area as deep a 7 kilometers below the ocean's surface that is believed to hold more than 50 billion barrels of oil.

"But if you put the price per barrel at five to six dollars, the government faces accusations that it is handing the oil over too cheap and benefiting foreign investors," said Adriano Pires, an oil expert at the Centro Brasileiro de Infraestrutura in Rio de Janeiro.

SHARES FALL

Preferred shares of Petrobras (PETR4.SA), the second most widely traded stock in Sao Paulo's Bovespa stock exchange, lost ground for a third day. The stock, down about 20 percent this year, tumbled 2 percent to 28.26 reais.

Voting shares of the company (PETR3.SA) fell for a fourth day, shedding 1.9 percent to 32.53 reais.

The issue of valuing the reserves has already created complications for the transaction, in which Petrobras will trade shares for up to 5 billion barrels of deep water oil and minority shareholders will buy stock.

The company in June rescheduled the deal for September after ANP said it would not have an independent estimate of the value of the oil until late August. Lima told local media that this timeline had not changed.

He said the capitalization plan could help the government increase its stake in the company's total capital. Currently the federal government has a majority of the voting shares but only a 32 percent stake in Petrobras' total capital.

Lima said that is too little.

"Who knows, we can fetch a 40 percent stake" in Petrobras, Folha quoted Lima as saying. (Additional reporting by Guillermo Parra-Bernal and James Matthews in Sao Paulo; Editing by Dave Zimmerman and John Wallace)