UPDATE 1-Brazil's BR Distribuidora beats profit estimates

(Adds details of earnings)

SAO PAULO, March 13 (Reuters) - Brazil's Petrobras Distribuidora SA beat fourth-quarter profit estimates on Tuesday, as the fuel distribution unit of state-run oil firm Petroleo Brasileiro SA defended strong profit margins despite slipping market share.

BR Distribuidora, as the company is known, posted net income of 531 million reais ($163 million), well above a consensus estimate compiled by Thomson Reuters of 294 million reais. Earnings before interest, taxes, depreciation and amortization, (EBITDA), totaled 980 million reais, above a consensus estimate of 890 million reais.

In its first earnings report since a December initial public offering, the company said its 2017 revenue slipped 5.7 percent from a year earlier to 43.27 billion reais.

Petrobras raked in north of 5 billion reais late last year when it floated a 30 percent stake in the unit as part of a bid to reduce the heftiest debt load among oil majors worldwide.

In a management statement, BR said revenue fell due to the strategy of preserving its profit margin regardless of its market share. Petrobras has lost market share in gasoline and diesel sales to rivals following a shift in 2016 to a policy of following international prices.

The move allowed Petrobras, with nearly 100 percent of Brazil's refining capacity, to boost profits even as it started to lose sales to rivals like Raizen and Ipiranga.

Though it has tweaked the policy, data in December showed Brazil imported more refined oil products in 2017 than in any year since records began in 2000, suggesting it has continued to lose ground to rivals.

($1 = 3.26 reais) (Reporting by Tatiana Bautzer and Roberto Samora Additional reporting by Alexandra Alper Editing by Sandra Maler and Chris Reese)