Ms Cooper criticised Moscow for its “provocative and reckless” violations of Nato air space in recent weeks during a speech to the United Nations.

It came as Mr Trump said Ukraine can win back all territory it has lost to Russia – a dramatic shift from his previous call on Kyiv to make concessions.

Ms Cooper told the United Nations Security Council meeting on Tuesday: “Ukraine’s security is our security, and all of us depend on upholding the UN Charter.

“Russia’s actions seek to undermine democracy, secure conflict and spread instability far beyond Europe’s borders.

“In recent weeks, we’ve seen provocative and reckless violations of Nato air space in Estonia, Poland and Romania, against which Nato stands firm, and we will be ready to act.”

Nato has said it will respond to Russian aeri

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