(Adds quotes from CFO, debt and cash information)

By Jeb Blount and Marta Nogueira

RIO DE JANEIRO, May 12 (Reuters) - Brazil's state-controlled oil company Petroleo Brasileiro SA posted its third-straight quarterly loss on Thursday as oil prices and production fell and a weaker currency boosted debt costs.

The result missed analyst expectations of a profit.

The consolidated net loss at Petrobras, as the company is known, was 1.25 billion reais ($358 million) in the three months ending March 31, compared with a profit of 5.33 billion reais a year earlier, the Rio de Janeiro-based company said in a securities filing.

The average estimate of five analysts surveyed by Reuters was for a profit of 3.64 billion reais.

Petrobras has struggled mightily with a plunge in world oil prices and its role at the center of a massive corruption scandal. It is saddled with the oil industry's largest debt and has also been hurt by falling domestic demand due to Brazil's worst recession since the 1930s.

That scandal helped lead to the removal of Brazilian President Dilma Rousseff, a former Petrobras chairwoman, earlier on Thursday by the country's Senate.

The average price of benchmark Brent crude oil fell 36 percent in the first quarter to $35.21 a barrel from $55.13 a barrel a year earlier. Efforts to reduce Petrobras' debt were also limited by an 11 decline in the value of Brazilian real against the U.S. dollar, raising the local currency cost of foreign debt.

"We want to increase our levels of predictability and meet our targets; when your debt is large and your risk increases you have fewer options," Chief Financial Officer Ivan Monteiro told reporters at Petrobras headquarters during an earnings presentation.

"Petrobras is a company with high cholesterol, and that cholesterol is debt leverage," he added, saying all senior executives are now focused on cutting costs and meeting targets.

Total debt was virtually unchanged from the fourth quarter at $126 billion. Rising debt maturities, though, dragged down Petrobras' cash position 21 percent to 77.8 billion reais from the end of 2015, according to the company's cash-flow statement.

High maturities are expected to last for at least three years, forcing Petrobras to limit investment, Monteiro said.

First quarter cash, though, was more than double the amount Petrobras had on hand a year earlier, thanks to lower capital spending.

Referring to possible debt swaps that could ease short and medium-term demands for cash, Monteiro said capital markets were "starting to offer alternatives to reduce the concentration of maturities."