WARSAW • US President Barack Obama yesterday urged Nato to stand firm against Russia over its seizure of Crimea from Ukraine, saying Britain's vote to leave the European Union (EU) should not weaken the Western defence alliance.

In an article in the Financial Times as he arrived for his last summit of the North Atlantic Treaty Organisation before leaving office in January, Mr Obama said the US' "special relationship" with Britain would survive the referendum decision. But he noted the vote had raised questions about the future of EU integration.

He added that the US will deploy 1,000 troops and a separate brigade headquarters to Poland, as the Nato alliance shores up its defences in eastern Europe. US troops in Poland are part of a larger Nato effort to deploy battalions to the Baltic states to reassure them.

Host nation Poland set the tone of mistrust of Russia, with Foreign Minister Witold Waszczykowski saying: "We have to reject any type of wishful thinking with regard to a pragmatic cooperation with Russia as long as it keeps on invading its neighbours."

Mr Obama urged dialogue with Russia but called on allies to keep sanctions on Moscow until it fully complies with a ceasefire agreement in Ukraine, and to help Kiev defend its sovereignty. Ukraine is not a member of Nato. "In Warsaw, we must reaffirm our determination - our duty under Article 5 of the North Atlantic Treaty - to defend every Nato ally," he said.

Estonia, Latvia, Lithuania and Poland - all Nato members - want a permanent Nato presence, fearing Moscow will seek to destabilise their pro-Western governments through cyber attacks.

The Kremlin said it was absurd for Nato to talk of any threat coming from Russia and it hoped "common sense" would prevail. Moscow was and remains open to dialogue with Nato and is ready to cooperate with it, it said.

Russia often depicts Nato as an aggressor, whose member states are moving troops further into former Soviet territory, which it regards as its sphere of influence.

REUTERS, AGENCE FRANCE-PRESSE