German chancellor Angela Merkel has warned that the Nord Stream 2 gas pipeline project can only go ahead if Ukraine’s role as a transit country for Russian gas is protected.

Her remarks suggested a hardening of the German position in relation to the $11.7 billion infrastructure project, which aims to double the amount of gas Russia can deliver via the Baltic Sea to Germany. The 1,200-km pipeline will run from Vyborg in Russia to Lubmin in Germany, allowing Russian gas producer Gazprom to circumvent the more costly route through Ukraine.

The new pipeline has been criticized by eastern European countries, which fear that Nord Stream 2 would increase European dependence on Russian gas at a time when political tensions with Moscow are on the rise. Several countries—most notably Ukraine—also stand to lose lucrative transit fees.

Speaking after a meeting with Petro Poroshenko, the Ukrainian president, in Berlin on April 10, Merkel acknowledged the concerns in unusually sharp tones. “It cannot be that Ukraine no longer has any relevance in terms of gas transit as a result of Nord Stream 2,” she told a press conference, stressing that she had made the same point in a telephone call with Russian president Vladimir Putin the previous day.

The chancellor added: “These are earnings for Ukraine. This has strategic importance for Ukraine. That is why I have made it very clear that the Nord Stream 2 project is not possible without clarity regarding the transit role of Ukraine.”

Last week, Alexei Miller, Gazprom CEO, was quoted by news agency Interfax predicting that his company would cut transit through Ukraine by a factor of 10 after Nord Stream 2 became operational.

“We are not saying that we will completely cut gas transit through the territory of Ukraine, as there are certain countries, regions, which are on the border with Ukraine from the side of Europe … We can talk about 10 to 15 billion cubic meters of gas per year,” Miller said.

Such plans threaten to erode sharply about $3 billion in annual transit revenues the war-scarred country earns from pumping gas to European markets and could make its vast pipeline not financially viable.

Germany has long sought to brush aside eastern European concerns over the new pipeline, insisting that Nord Stream 2 was above all an economic project led by the private sector. On April 10, however, Merkel qualified that assessment: “This is not just an economic project. Political factors also have to be considered.”

Her remarks stopped short of a full-blown German reversal on the project, which is due to be completed toward the end of next year. But they do suggest a greater willingness to ensure that eastern European interests would not be ignored as Nord Stream 2 moved closer to completion. Merkel’s intervention follows a series of unusually critical statements toward Russia made by Heiko Maas, Germany’s new foreign minister.

Nord Stream 2 has been a contentious political issue in Germany, in part because the consortium is chaired by Gerhard Schröder, the former German chancellor and ex-leader of the Social Democratic party.