The warning comes as President Dilma Rousseff is battling to protect Brazil's coveted investment grade rating with a series of market-friendly measures — efforts that could be obscured by the prospect of bailing out Petrobras, Mr Leos said.
With more than $139bn in total debt, Petrobras ranks as the world's most indebted oil producer, but it retains an investment grade credit rating.
In November police arrested almost 30 executives from Petrobras and Brazil's largest construction firms, including the head of OAS, for their alleged involvement in a multibillion-dollar kickback scheme — the largest in Brazil's history. They are accused of conspiring to inflate the value of Petrobras contracts by up to 3 per cent to pay bribes and funnel cash to the ruling Workers Party (PT) and its allies.
Read MorePetrobras scandal is shaking Brazil
Petrobras has said that it is co-operating with the authorities, while OAS declined to comment on its alleged involvement. After missing a $16m interest payment on Friday, OAS failed to pay R$100m ($37m) in principal and interest on local bonds on Monday, leading rating agencies to predict a default by the company. OAS, which had R$6bn in net debt by the end of the third quarter, said that it is preparing a restructuring plan and intends to sell assets to increase liquidity.
"I see some other names facing the same lack of liquidity and difficulty accessing lines of credit," said Marcelo Lima, a fixed income trading manager at INTL FCStone in São Paulo. "OAS missing the payments also makes it even harder for any other company to access the foreign market," he said.
Late last month Petrobras froze payments to OAS and 22 other contractors linked to the investigation.
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If Petrobras loses its investment grade rating that could also have a "snowball effect" on companies with links to the oil firm, said Carlos Gribel, head of fixed income at Andbanc Brokerage in Miami.
Petrobras has yet to release its third-quarter results, preventing it from accessing capital markets and prompting concerns that it could be declared in technical default, possibly forcing the early repayment of debts.
However, late on Tuesday Petrobras said that an unidentified group of creditors had agreed to accept its unaudited rather audited statements, which are set to be released by the end of this month.