Brazil has discovered what could be the third biggest oil reserve in the world, according to the head of the country's National Petroleum Agency.

The deep-sea find by state-run oil firm Petrobras could yield 33 billion barrels in reserves.

Further tests are required to assess the scale of the find, off the coast of Rio de Janeiro, but analysts say it could have significant implications.

Brazil announced sizeable new gas and oil discoveries last year as well.

'Big number'

In December 2007, Brazil said it had found a new reserve in the Espirito Santo region a month after a reserve in the nearby Tupi oil field of up to eight billion barrels was found.

According to the US Energy Department, Brazil's existing proven oil reserves total 11.8 billion barrels, while the US holds 21.8 billion.

Referring to the latest discovery, Citigroup analyst Tim Evans said: "It's a big, big number".

Petrobras said "more conclusive data" about the potential of the discovery would only be known after further evaluation.

A spokesperson for the National Petroleum Agency said the statement by its president Harold Lima about the find was based on unconfirmed sources.

Even if the reserves are proven, it is likely to take ten years before the latest find can be turned into significant supplies.