The EU executive called on Ukraine, whose president is due to inaugurate the Bystroye on Thursday, to immediately halt work on the project until a study has been carried out into its environmental impact on the delta, a UNESCO World Heritage Site.

"The European Commission deeply regrets the ... opening to navigation of the initial part of the Bystroye canal between the River Danube and the Black Sea," the European Union's executive arm said.

"It's not a welcome development. The opening of this canal is not going to help our relations with Ukraine," said Commission spokesman Jean-Christophe Filori.

The delta contains one of the world's most important wetlands and is a breeding and feeding ground for many endangered species of bird. Environmentalists fear the canal could disrupt the area's delicate ecosystem.

The first section of the canal, which will give Ukraine navigable access to the Black Sea, is due to be officially opened on Thursday at a ceremony attended by Ukrainian President Leonid Kuchma.

The canal is scheduled to go into operation by the end of this year, although construction work will continue until 2008.

Romania, the United States and environmental groups have also protested to Kiev about the project in the delta, which straddles the Ukraine-Romania border. The delta's nature reserve was labelled a global treasure by the UN Educational, Scientific and Cultural Organisation (UNESCO) in 1991.

On Monday Bucharest asked the United Nations to set up a commission to evaluate the environmental impact of the canal, and Washington voiced "deep concern" about the possible environmental consequences.

But Ukraine reacted on Wednesday by dismissing these concerns and accusing Romania of exaggerating the potential dangers.

"We see no reason to worry about ... the presumed danger this canal poses for the ecology of the region," said Ukranian foreign ministry spokesman Markian Lubkivsky.

Lubkivsky said Ukraine had "submitted all the necessary material on this project to its US and European partners". "Since then we have not received any new request for information," he alleged.

In Brussels the Commission said it would welcome "reassurances from (Ukraine) confirming its intention not to proceed further with this project pending preparation of a proper Environmental Impact Assessment to international standards".

The canal row casts a new cloud over Kiev's relations with the enlarging EU, which includes Ukraine in its "European Neighbourhood" policy designed to promote better ties with ex-Soviet states on its eastern borders.

On May 1 this year, when the EU expanded from 15 to 25 member states -- with Romania and Bulgaria lined up to join in 2007 -- Ukraine reiterated its desire one day to join the "family of European nations".

But at an EU-Ukraine summit in July the European bloc refused to grant Ukraine market economy status, citing lack of promises to make social, economic and civil rights reforms.

The Commission said Wednesday that the EU raised the canal issue at the July summit. "They listened carefully to what we had to say, and they promised to take it into consideration.

"But apparently it had limited effect, to say the least," said the spokesman.

TERRA.WIRE