BERLIN (Reuters) - A key ally of German Chancellor Angela Merkel on Monday raised questions about the future of the Nord Stream 2 gas pipeline amid growing concern about Russia’s seizure of three Ukrainian ships and their crew off the coast of Russian-annexed Crimea.

Juergen Hardt, foreign policy spokesman for Merkel’s conservatives in parliament, told Reuters that further sanctions against Russia would have to be considered unless diplomatic efforts were able to resolve the conflict.

“When diplomatic efforts to ease tensions fail, we cannot ignore the question of whether it is responsible to further increase the dependence of Germany and the European Union on Russia gas,” he said. “Without increased trust in Russian policies, Nord Stream 2 will become a mistaken investment in economic and policy terms.”