WARSAW (AFP) - Germany's reliance on Russian natural gas poses a threat to European sovereignty, Polish Prime Minister Donald Tusk warned Monday amid rising East-West tensions over Ukraine.

"Germany's reliance on Russian gas can effectively limit European sovereignty. I have no doubt," Mr Tusk told reporters, days ahead of a Warsaw visit by German Chancellor Angela Merkel.

The top European economy buys around one third of its oil and gas from Russia and has extensive trade and investment links with the vast country to the east.

Germany has tried to defuse the Western standoff with Moscow over Ukraine, but analysts say its voice is muted by fears of endangering its economic ties with Russia.

"The Ukraine issue is a matter of the future security of the European Union," Mr Tusk said on a visit to a military base in northern Poland to mark 15 years since his ex-communist nation joined the Nato defence alliance.

The 28-member EU needs to review its energy policy, he added, ahead of Ms Merkel's Wednesday visit.

"I'll be speaking very openly with Merkel, making it clear that the existing climate and natural gas policies risk posing a threat to the security and sovereignty of Europe as a whole," he said.

"I'll present our views on the political threats tied to dependence on Russian gas and money," Mr Tusk said. "This, of course, applies not just to Germany, but in recent years Germany has been a strong example of this phenomenon," he added.

Mr Tusk said talks with Ms Merkel would also focus on "how Germany could revise certain economic decisions, to avoid the paralysis of Europe at a time when it must act quickly and adopt a clear stance".

Washington on Friday played down the risk posed to the European economy by Russia's threat to cut off gas supplies to Ukraine, insisting the region had adequate stocks.

Russia is Europe's biggest single energy supplier and its natural gas pipelines mainly run through Ukraine, where some is used and some passes through to major Western economies such as Germany.

Washington, which backs Ukraine's interim government and opposes Moscow's moves to seize the Crimean peninsula, said any gas embargo would hurt Moscow as much as Kiev.