The US Air Force has chosen a Brazilian firm for a $427 million contract to supply light attack planes to Afghan forces, the company said Thursday, despite competition from an American bid.

Brazilian planemaker Embraer said 20 of its AT-29 Super Tucano aircraft would be manufactured in Florida in partnership with an American firm, after winning a prolonged competition with US rival Hawker Beechcraft Corp.

US forces are due to withdraw from Afghanistan next year, leaving the Afghan military to continue the fight against Taliban rebels, and Washington is racing to train and equip its lightly-armed allies for the battle ahead.

"The A-29 Super Tucano with its proven track record is exactly what's needed," said Taco Gilbert, a vice-president of Embraer's US partner in the contract, the Sierra Nevada Corporation (SNC)

The propeller-driven Super Tucano comes in single and two-seated versions that can be equipped with a machinegun and a variety of bombs and missiles, in a ground attack or reconnaissance role.

Embraer and Sierra Nevada were initially awarded a $355 million contract for the planes in December 2011, but the US Air Force called off the deal two months later after a legal challenge from rival Hawker Beechcraft.