The company has already invested $11bn for the first unit of the refinery, which is more than 82% complete in ItaboraĆ­, Brazil. The additional investment takes the total cost to $15.3bn.

Petrobras refining chief Jorge Celestino Ramos was quoted by Reuters as saying during hearings at the Rio de Janeiro-state legislature that the company is seeking potential partner to commission the first unit at the refinery before 2020.

According to Petrobras, the refinery was planned to be commissioned in August 2016.

The 165,000 barrel-a-day unit was initialed scheduled to be completed in 2013 but the plan was later deferred to September 2014, due to delays in contracting utilities.

In addition, a corruption scandal in late 2014 that raised concern about overspending and bribery in refining projects compelled Petrobras to halt all work at Comperj refinery.

Comperj will have an estimated cost of about $93,000 for each barrel of refining capacity added.

The refinery is designed to meet the demand for oil products such as diesel fuel, petrochemical naphtha, jet fuel, coke and LPG in the country.