Brussels  - The European Union issued a cautious reaction Sunday to the news that Russia and Ukraine had reached a deal on resuming gas supplies to Europe.

"The (European) Commission welcomes the announcement in Moscow of Prime Minister (Vladimir) Putin and Prime Minister (Yulia) Tymoshenko, and in particular the announcement that gas transit to Europe could be resumed on Monday," the EU's executive arm in Brussels said in a statement.

"But we have seen many false dawns in this dispute, and the 'test' in this case is whether or not the gas flows to Europe's consumers. Until that point, the wait goes on for Europe," the statement said.

Putin and Tymoshenko were set to sign documents ending the crisis - which has blocked shipments of Russian gas to Ukraine and much of Western Europe since the start of the year - on Monday, following intense discussions in Moscow.

But even if supplies do resume on Monday, experts say it could take up to three days for the gas to reach European customers and for pressure to return to normal in pipelines.

The commission and the Czech presidency of the EU had issued a series of statements over the past weeks warning Ukraine and Russia that their credibility as reliable gas suppliers risked being irreparably damaged if the standoff was not resolved quickly.

Officials in Brussels had already anticipated a quick solution to the crisis when representatives from the two countries' state-owned energy companies, Russia's Gazprom and Ukraine's Naftogaz, promised to resume supplies on Tuesday following a monitoring deal signed last Monday in Brussels.

Europe receives a quarter of its gas imports from Russia - 80 per cent of which flows through Ukrainian pipelines.

It was still unclear Sunday if Tymoshenko had the backing of her political rival Ukrainian President Viktor Yushchenko for the deal she negotiated in Moscow. dpa