Reuters also reported in February that Boeing has frozen the price on its bid since 2009, an unusual step that is believed to have amplified the F-18’s cost advantage over the Rafale. The per-unit cost of the jets has not been made public.

“Boeing is definitely looking better in the last few months,” a second official said.

Saab is still seen as a distant third in the talks, both officials said.

Defense officials say Rousseff must make a decision soon because the existing Brazilian Air Force fleet is becoming increasingly obsolete and expensive to maintain. Brazil is also under pressure to increase its defense capabilities as it prepares to host the 2014 World Cup and 2016 Olympic Games.