The Boeing plane, an icon of the Cold War with its distinctive saucer-shaped radar dome mounted on the fuselage, began NATO service in 1982 and is due to be phased out by 2035.

But the alliance has not yet decided what will replace AWACS, which has seen NATO service during the first Gulf War, the 1990s conflicts in the former Yugoslavia, Afghanistan and most recently supporting the fight against the Islamic State group.

"I can confirm we will sign a contract upgrading, modernising the AWACS fleet -- $1 billion dollars," NATO chief Jens Stoltenberg told reporters at a meeting of foreign ministers in Brussels.

"We are also now looking how to replace the AWACS fleet in the future after 2035."

The fleet of 14 AWACS planes -- Boeing 707s converted with long-range radar and sensors to give early warning of aircraft, helicopters and missiles -- is the only military equipment NATO itself owns.

Since its inception, the AWACS programme has already cost NATO more than $6.8 billion.

Stoltenberg also confirmed that NATO would soon receive its first Global Hawk high-altitude surveillance drones, which will give commanders on the ground a better picture of combat situations.

pdw/rmb/jj

BOEING