BRUSSELS/KIEV, January 7 (RIA Novosti) - As a complete shutoff in Russian gas deliveries to Europe via Ukraine deepened supply problems across the continent on Wednesday, the European Union called for transfers to resume.

Ukrainian President Viktor Yushchenko urged on Wednesday that Russia restart the transit of gas to Europe via Ukraine.

The fourth and final pipeline carrying Russian gas across Ukraine was shut off early Wednesday morning, with Gazprom and Kiev blaming each other for the closure. A deputy head of Gazprom warned that the break in supplies could damage the pipelines.

A Czech source in Brussels told RIA Novosti that the EU was calling on both sides to honor their contractual obligations for the delivery of gas. The Czech Republic took over the rotating presidency of the EU on January 1, the day Ukraine's contract for Russian gas supplies expired.

Talks between Russia and Ukraine ended on New Year's Eve with no agreement on how to settle Kiev's gas debts or on a contract for 2009 deliveries. European consumers of Russian gas quickly became embroiled in the dispute as supplies via Ukraine were disrupted and on Wednesday finally halted.

"We are calling on both sides to renew gas supplies without delay and to fulfill their obligations," the Czech official said.

Yushchenko invited EU officials to visit the transit points and the control room for its pipeline network to monitor what was happening.

In a letter to Russian President Dmitry Medvedev and European Commission head Jose Manuel Barroso published on the Ukrainian president's web site, Yushchenko says Kiev "is extremely worried by the situation" and can immediately restart negotiations.

The letter says that Ukraine "does everything possible to ensure transit" of Russian gas, even using Ukrainian gas from underground reservoirs. Describing the situation in Europe as "dangerous," Yushchenko called on Medvedev "to step back from any arbitrary cuts in gas supplies to European users."

Gazprom warned that the empty pipes could be damaged by the freezing temperatures.

"In the cold weather, the absence of gas flow through the [gas transportation] system could cause plugs along the system, which could require very serious operations, including new tap-ins," Gazprom deputy head Alexander Medvedev said on the Vesti TV news channel.

"I don't even want to think about it, but we have to reveal the dangers of such irresponsible behavior by the Ukrainian side," he said.

The latest closure added Austria, the Czech Republic, Romania and Slovakia to the list of countries receiving no Russian gas. The three other pipelines were closed on Tuesday, ending deliveries via Ukraine to Hungary, Serbia, Macedonia, Croatia, Bulgaria, Turkey, Greece and Bosnia. Supplies to Italy, Poland, France and Slovenia are seriously disrupted.

Negotiations are due to resume on Thursday, with Naftogaz CEO Oleh Dubyna due in Moscow for talks with Gazprom chief Alexei Miller. Dubyna said Ukraine was unlikely to agree to pay $450 for 1,000 cubic meters of Russian natural gas, a price mentioned by Miller in the past.

"We will resume the talks," he said. "I am not ready to predict how the talks will go."