Poland's defence minister has condemned a gas pipeline project which will link Russia and Germany via the Baltic Sea but bypass Poland.
Poland says it should have been consulted before the deal
Radek Sikorski reportedly compared the deal to a pre-World War II Nazi-Soviet pact dividing up Poland.
He said the move by Germany raised questions about the feasibility of a common European foreign policy.
The $5bn (£2.7bn) pipeline, agreed in September 2005, will connect Babayevo in Russia to Greifswald in Germany.
The 1,200km (744 mile) pipeline is now under construction and will deliver Russian gas to Germany - and eventually to other Western European nations - by 2010.
But it is set to bypass Poland, prompting concern in Warsaw that the new pipeline could be used to divert energy away from Poland for political purposes.
'Deals above our head'
Speaking at an international conference in Brussels, Mr Sikorski said the move by Germany did not bode well for plans for more integrated European Union cooperation on foreign and security affairs.
He said Germany should have consulted Poland before the deal. "Taking the decision first and consulting us later is not our idea of solidarity," he said.
Poland was sensitive to "deals above our head", he said.
"That was the Locarno tradition, that was the Molotov-Ribbentrop tradition," he said, quoted by Reuters news agency, referring to a 1939 pact between Stalin and Hitler which divided Poland up between Russia and Germany.
And he explained why Poland was worried. "The Russian ambassador to Belarus said last week when the Baltic pipeline is built, Gazprom will be able to cut off Belarus without cutting off Germany. That means Poland too."
The BBC's Jonathan Marcus says energy security is now one of the principal issues driving international diplomacy.
Russia's emergence as an energy superpower, ready and willing to use its market strength as a diplomatic tool, makes less powerful countries like Poland worried, he says.
The Baltic pipeline episode underscores the difficulty of separating energy diplomacy from old-fashioned power politics, our correspondent says.