BRUSSELS (Reuters) - Poland should refrain from building a canal on its Baltic coast before it gets approval from European Commission, an EU official said, after Warsaw failed to assuage the bloc’s concerns about the project during talks in Brussels on Friday.

The case risks becoming the next flashpoint between Poland’s ruling nationalists and the EU, their relationship already strained by disputes over the rule of law and migration.

It concerns cutting through a thin, heavily wooded sandbank called the Vistula Spit, 55 km (34 miles) long but less than 2 km wide, which encloses a coastal lagoon shared with the neighboring Russian enclave of Kaliningrad.

Currently, the only access to the lagoon from the Baltic Sea is a channel at the Russian end of the spit. Warsaw says the canal is needed for both security and economic reasons.

The Polish government said after the meeting that the European Commission “confirmed the necessity of building a navigation canal through the Vistula Spit but asked to continue talks to discuss technical matters”.

But an EU official denied that, saying: “The Commission services did not confirm the need for this project.”

“The Commission services will assess the additional information provided by the Polish authorities and the technical discussions will continue,” the official added.

“Pending a final Commission decision ... no works should be undertaken.”

The European Commission, which checks policies and projects by EU states against the bloc’s laws, has raised concerns about the planned canal, some of them environmental.

Poland has not yet started large-scale construction but has been preparing the area, including by felling trees in a way that critics say may violate EU laws on protecting wildlife.