Portugal could acquire six Embraer KC-390 tactical transports following the signature of a declaration of intent by defence minister Augusto Santos Silva and his Brazilian counterpart Nelson Jobim.
Lisbon's show of support further strengthens Embraer's developmental KC-390, coming swiftly after Chile and Colombia made similar commitments to the programme worth a combined 18 aircraft.
"The agreement marks the beginning of negotiations for Portuguese companies to join the project and to participate in the manufacture of the new airplane, as well as the future acquisition of six aircraft for the Portuguese air force," says Embraer.
"We have strong historic ties of bilateral co-operation with Portugal, and are very enthusiastic about their future participation in the KC-390 programme, which will contribute decisively to strengthening that country's aeronautics cluster," says company chief executive Frederico Fleury Curado.
The Brazilian air force is expected to be the launch operator of the KC-390 twinjet, with the service having identified an initial requirement for 28 examples. Embraer has yet to freeze the tanker/transport's final design configuration, or to confirm its main equipment suppliers.
Portugal's commitment represents a blow to Airbus Military, which assembles the A400M in neighbouring Spain. Lisbon was previously interested in the larger design, but withdrew from the European programme before its formal launch in 2003.
The Portuguese air force already operates 15 of Airbus Military's C-212 light and C-295 medium transports, plus six Lockheed Martin C-130H Hercules, as listed in Flightglobal's MiliCAS database.