Russia and Ukraine faced another day of sparring over gas supplies yesterday and two European Union states, cut off for a freezing week by the row, launched missions to plead for Russian gas flow to be restored.
European Commission chief Jose Manuel Barroso called the crisis "unacceptable and incredible" and warned the EU executive would advise the bloc's firms to sue Russian and Ukrainian energy companies unless gas supplies were restored quickly.
Russia began pumping gas meant for Europe via Ukraine on Tuesday, but the EU said little or no gas was flowing yet to other countries downstream suffering urgent energy shortages.
Russia accused Ukraine of deliberately cutting gas to Europe, but Kiev said Russia had so far provided so little gas there was not enough pressure in the pipelines to pump it on.
"Such small volumes... do not allow for further transportation of gas as there is insufficient pressure," Prime Minister Yulia Tymoshenko told a Cabinet meeting.
The crisis has hit 18 countries in the depths of winter, shutting down many factories and leaving householders shivering.
"If the agreement sponsored by the EU is not honoured, the Commission will advise EU companies to take this matter to the courts," Mr Barroso told the European Parliament.
"The current situation is in short most unacceptable and incredible," he said. "If the agreement is not honoured, it means that Russia and Ukraine can no longer be regarded as reliable."
Two of the worst-hit EU states, Bulgaria and Slovakia, sent their prime ministers to Moscow and Kiev in a fresh effort to get gas supplies restored.
Slovakian Prime Minister Robert Fico said his country had 11 days of gas reserves left.
"After 12 days, we will be obliged to resort to measures never seen in our history. May I simply ask how long this will go on?" he asked Ukraine's Tymoshenko.
Slovakia, which gets almost all its gas from Russia, declared a state of emergency on January 6, under which gas deliveries to large clients were reduced. About 1,000 companies were forced to shut or cut production.
Ms Tymoshenko said her country could do little to help. "Ukraine does not have sufficient gas. We do not have our own supplies," she told Mr Fico who said he was passing on to Ms Tymoshenko a request by the Czech Republic, which holds the rotating presidency of the EU, for talks between the premiers of Ukraine and Russia on restoring gas supplies to Europe.
Mr Fico is due in Moscow to meet Russian Prime Minister Vladimir Putin alongside Bulgarian Prime Minister Sergei Stanishev and Moldovan Prime Minister Zinaida Greceanii.
Mr Stanishev is under pressure to secure supplies for his country as domestic reserves are dwindling and public anger is mounting against his Socialist-led government.