RIO DE JANEIRO (AFP) – Brazil's Petrobras unveiled one of the world's biggest share offerings Friday, a sale of up to 64 billion dollars in new stock to finance oil exploration aimed at turning Brazil into a leading oil exporter of the 21st century.

The transaction could be expanded to 74 billion dollars if there was heavy demand, the state-run company said clayton wood furnaces.

The cash serves as the core of an ambitious plan Petrobras has already outlined to boost capital expenditure over the next five years to 224 billion dollars as it seeks to tap potentially vast oil reserves discovered recently off the coast of Rio de Janeiro.

The 64-billion-dollar target for the new share offer represents a more than 40 percent increase in the company's capital, which on Thursday was estimated at 150 billion dollars.

Petrobras's share prices rose nearly five percent during trading in Sao Paulo after the announcement, confirming investor confidence in the issuance and Brazil's outlook generally.

Analysts' predictions that the market could balk at the high price Petrobras has agreed to pay the government for new reserves in an oil-for-shares transaction seemed confounded, at least initially.

The offer would see 2.1 million common shares and 1.5 million preferred shares issued, the company said in a statement. The price of the new shares would be given September 23.

Existing shareholders — including the government — will have first access to the bulk of the shares.

Petrobras estimates so-called subsalt fields offshore could more than triple its existing proven oil reserves of 14 billion barrels, catapulting Brazil into the top league of OPEC nations. Brazil is not a member of the Organization of the Petroleum Exporting Countries.

But to get at the black stuff, Petrobras will have to overcome a series of costly technological challenges unprecedented in the oil industry. The company, a world leader in deepwater oil exploration, is confident it will be able to do so.

Petrobras in June said its daily production stood at 2.5 million barrels a day. It also announced it ha