Poland and Ukraine plan to act jointly to block projects that could result in Russia's Gazprom gaining greater access to the European gas market by bypassing Ukraine, Ukrainian President Petro Poroshenko said on Friday.
In October the European Union lifted a cap on Gazprom's use of the Opal pipeline which carries gas from the Nord Stream pipeline that crosses the Baltic Sea to end-users in Germany and the Czech Republic.
That decision opens the way for Russian plans to expand Nord Stream's capacity and bypass Ukraine as a gas transit route.
Poland, which imports most of the gas it consumes from Russia, immediately criticised the Commission's move saying it threatens gas supplies to central and eastern Europe.
Ukraine has not bought gas from Russia for about a year due to a political stand-off with Moscow, which annexed Ukraine's Crimea in 2014.
Chief Executive Officer at Polish state-run gas firm PGNiG Piotr Wozniak had planned to visit Ukraine in November to discuss a joint response to the Opal decision.
Earlier this week a local daily quoted Wozniak as suggesting the Commission's decisions are contradictory, keeping EU sanctions on Russia while reinforcing Gazprom's gas monopoly which he says helps Russia's "war budget".
On Friday the presidents of Poland and Ukraine advocated a review of the Commission's decision on Opal but acknowledged in a joint statement that could be "very difficult and painful".
"We do not support the European Commission's decisions regarding the Opal link and the construction of Nord Stream 2," Poroshenko said at a joint conference with Poland's president Andrzej Duda in Warsaw.
"We have decided to coordinate our actions in order not to allow these projects to take place," Poroshenko also said.
Duda told the same conference Poland supports Ukraine in its fight for sovereignty.
Analysts are sceptical though about Poland's and Ukraine's plans to stop Gazprom's expansion in Europe.
"These objections now remind me of those when Nord Stream 1 was built. I think the recent EU decisions show that the new gas link (NS2) will be built and no pressure or lawsuits will help," oil and gas expert Andrzej Szczesniak said, adding Poland and Ukraine cannot count on much backing from other parties.
"Business is business and politics is politics, but this is not well understood in Poland," he added.
PGNiG said it will unveil details of its legal actions against the EU decision on Monday.