RIO DE JANEIRO, Feb 5 - Brazil's state-controlled oil company, Petrobras, has recently expanded to one year, from three months, the period for which it calculates the international price parity of the fuels it sells, two people familiar with the decision said.

The change, which applies to both diesel and gasoline, avoids transferring international price volatility to local gas pump prices, said the people, who declined to be named because the information is not public.

Petrobras, as the state-controlled company is known, did not immediately respond to a request for comment.

The shift was made in the second half of December, the people said, amid increased threats by truckers to go on national strike against high diesel prices.

Petrobras Chief Executive Officer Roberto Castello Branco has said last week demands by truckers are not his problem and said there is no government interference.

(Reporting by Sabrina Valle in Rio de Janeiro Editing by Matthew Lewis)