The leaders of gas-starved European nations pressed Ukraine and Russia to restore energy supplies immediately Wednesday and the European Union threatened that they both could be sued for ripping apart the continent's winter-heating plans. But the natural-gas drought persisted along with virulent, mutual recriminations bet-ween Russia and Ukraine. In an indication that no resolution was on the horizon, Russian President Dmitry Medvedev proposed that European gas-consuming nations send their leaders to Moscow for a summit this Saturday. The prime ministers of Bulgaria and Slovakia - among the hardest-hit nations - showed up in Moscow and Kiev even before the summit call. "Millions of Europeans feel like hostages and are truly suffering," Bulgarian Prime Minister Sergei Stanishev told Vladimir Putin as he visited the Russian prime minister's home outside Moscow with his counterparts from Slovakia and Moldova. Both Medvedev and Putin accused Ukraine of being responsible for holding Europe hostage, while Kiev said Russia was deliberately erecting technical obstacles to delivering gas to Europe through Ukrainian pipelines. Ukrainian President Viktor Yushchenko insisted the Russian gas monopoly Gazprom was trying to charge Ukraine an unjustly high price for gas in order to drive it into debt and acquire a stake in Ukraine's vast pipeline network. Visiting Poland on Wednesday, Yushchenko vowed he would never let that happen. Calling the situation "incredible," European Commission President Jose Manuel Barroso warned Gazprom and Ukraine's state-run company Naftogaz he would urge European energy companies to sue them unless the dispute is resolved quickly. "If the agreement is not honored, it means that Russia and Ukraine can no longer be considered reliable partners for the European Union in matters of energy supply," Barroso told the European Parliament. The crisis has deepened European concerns about Russia's willingness to use its energy riches as a political tool and raised questions about the reliability of Ukraine, whose pro-Western leaders want to join the EU but are mired in dangerous disputes with Russia. European Union countries had hoped supplies would be restored Tuesday after they brokered a deal sending EU monitors to keep tabs on the flow of gas. Europe relies on Russia for about a quarter of its gas, 80 percent of that delivered via Ukraine. But while Gazprom resumed some gas supplies, Ukraine did not send the gas on to Europe, saying the route that Gazprom demanded would force Ukraine to halt domestic gas supplies to a large swath of territory. The same thing happened again Wednesday, said Oleh Dubina, the head of Naftogaz. "Unfortunately, we answered the same way: we cannot leave our regions without gas," he said. Putin said it was up to Ukraine to make the deliveries possible. "We opened the tap, and are ready to supply gas, but on the other side, the tap is closed," he told the visiting prime ministers. "Nobody, no transit country, has the right to abuse its transit location to take other customers hostage." Bulgaria has lost all its gas supplies, and Slovakia nearly all. "Ukraine is losing the trust of European partners because of its behavior," Slovakian Prime Minister Robert Fico said. Medvedev said Gazprom should sue Ukraine over what Gazprom chief Alexei Miller told him was $1.1 billion in lost income. Russia and Gazprom "cannot lose so much money in the current conditions," Medvedev told Miller in televised comments, referring to the global financial crisis. Gazprom cut off all gas supplies meant for Ukrainian consumption on January 1, amid a price dispute. It stopped sending any gas at all into Ukraine's pipeline system on January 7, alleging that Ukraine was siphoning off supplies destined for Europe. Ukraine has denied the charges, claiming that Russia has not sent enough so-called "technical gas" to pump the rest of the gas west to Europe. Who pays for the technical gas is also in dispute - and the amount used by Ukraine's sprawling, inefficient system runs into millions of dollars each day. The clash has affected millions of people, mostly in eastern Europe, in the midst of winter. Thousands of businesses have had to shut down or cut production, forcing workers into involuntary layoffs. Underlying the energy dispute is a struggle between Russia and the West over the future of Ukraine, whose leaders have angered Russia by pressing for integration with NATO, supporting Georgia in its August war with Russia and threatening to evict a Russian naval base within a decade.