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STORY: At a NATO summit in Madrid, Biden also underscored the Atlantic alliance's commitment to "defend every inch" of its territory.

"We mean it when we say an attack against one is an attack against all," he told reporters at the start of a meeting with NATO Secretary-General Jens Stoltenberg.

Biden said Washington would work with Spain to raise the number of U.S. destroyers based in Rota, Spain to six from four, and send two additional F-35 squadrons to Britain.

Leaders of NATO countries were meeting in the Spanish capital Madrid to thrash out policy in response to Russian actions, and also to any Chinese threat.