All three countries are NATO members, and the sale of F-16 fighters to Slovakia will enable it to retire its Russian-built MiG-29s and build a fleet to work with its Western allies.

US President Donald Trump has called on all NATO members to increase their defense spending and thus better distribute the burden of paying for the alliance's collective security.

The total coast of Slovakia's package -- 14 jets plus spare parts, air-to-air missiles, guided bombs and US contractors to train local crews -- will come to $2.91 billion.

"Slovakia's current fighters are not interoperable with US forces or regional allies," the US Defense Security Cooperation Agency said, in a statement.

"Purchase of the F-16V will provide Slovakia with fourth-generation fighter aircraft capability that is interoperable with the United States and NATO," it added.

US defense contractor Lockheed Martin and its suppliers and sub-contractors will receive the bulk of the spending.

Meanwhile, longstanding NATO member Spain has been approved to spend $1.3 billion to buy seventeen CH-47F Chinook heavy-lift helicopters from US aerospace giant Boeing.

And Britain plans to spend $500 million with General Dynamics on the firm's MQ-9 Reaper, an unmanned plane that allows remote operators to carry out reconnaissance or fire missiles.

British forces adopted the Reaper in order to work alongside their US allies in Afghanistan and the contract covers support and maintenance as it becomes part of their standard fleet.

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BOEING

LOCKHEED MARTIN

GENERAL DYNAMICS