European Union leaders have warned against trying to "circumvent" EUsanctions against Russia and say they will close any "loopholes" that are found.
At a top-level summit in Brussels the 27 presidents and prime ministers said any attempts to get around restrictions imposed by the block "must be stopped".
The blunt warning came in the early hours of the morning on Friday after a discussion of the situation in Ukraine dragged late into the night.
Leaders are meeting again on Friday where they will consider more sanctions, with a possible phased-in ban on Russian oil and coal an option on the table.
But the 27 countries are not expected to approve the biggest sanction: a ban on Russian gas, which some EU countries like Germany and Italy are heavily dependent on.
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Alexander de Croo, the Belgian prime minister, told reporters on the doorstep of the summit: "Measures on energy right now would have a huge impact on our economies.
“The basic rule is that sanctions must have a much greater impact on the Russian side than on the European side. We don't wage war on ourselves."
Meanwhile Mark Rutte, the Dutch leader said: “Everybody wants it but it’s nothing that you can do in the short term."
The cautious approach is expected despite signals from the US that it will ramp up natural gas shipments to Europe – a promise relayed by Joe Biden while he visits the EU capital.
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Biden to visit Poland, a complex ally on Ukraine's doorstep Poland Biden Visit Poland Biden Visit
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It comes after Russia demanded to be paid for its gas in Roubles instead of Euros – which the European Commission considers an attempt to work around sanctions.
“This would be a unilateral decision and a clear breach of contract,” Von der Leyen said of Russia’s demand.
“It would be an attempt to circumvent the sanctions. We will not allow our sanctions to be circumvented. The time when energy could be used to blackmail us is over.”
The Council summit comes after a Nato meeting to decide a common defence approach to help Ukraine and shore-up militaries in Eastern Europe.
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Boris Johnson attended the Nato summit for the UK but Britain is not invited to the European Council meeting, and it no longer has an automatic seat due to Brexit.
Mr Biden was hosted by EU leaders as a special guest given the situation in Ukraine.