German chancellor Angela Merkel opposes NATO membership for Ukraine and worries that a planned referendum in the country about joining the alliance could aggravate Western relations with Russia.

The Bloomberg news agency cites a German official saying Merkel believes the referendum won’t bring Ukraine closer to NATO. A second official said any Ukrainian bid to join NATO could only end badly. Both asked not to be named.

Michael Grosse-Brömer, the parliamentary whip for Merkel’s Christian Democratic bloc, said, “NATO membership for Ukraine isn’t on the agenda at this point.”

Foreign minister Frank-Walter Steinmeier similarly told Der Spiegel magazine last week that Ukrainian NATO membership would be a “project of the next few generations.”

However, Jens Stoltenberg, the NATO chief, said Monday the door was still open. “Ukraine will become a member,” he said. “That decision still stands providing that Ukraine meets the requirements.”

NATO agreed in 2008 that former Soviet republics Georgia and Ukraine would ultimately join. But France and Germany blocked plans at the time to actually start their accession process.

The prospect of Ukraine, the largest of Russia’s former Soviet republics, joining the Western alliance is believed to have motivated President Vladimir Putin’s takeover of the Crimea in March. The peninsula, which was joined with what was then the Ukrainian Soviet Socialist Republic in 1954, headquarters Russia’s Black Sea Fleet.

Russia has since supported a separatist uprising in the southeastern Donbas region of Ukraine although Putin’s administration denies Western accusations that it has given the rebels weapons.

Putin’s policy has shifted Ukrainians decidedly in favor of seeking closer relations with the West. A new five-party government, elected last month, has made meeting the conditions for both European Union and NATO membership part of its program.

Germany was originally seen as reluctant to confront Russia over its aggression in Ukraine. Perceptions hardened with the Donbas rebels downed a commercial airliner in July and Russia shifted responsibility to the government in Kiev. Western powers later doubled down on their economic sanctions against Russia which have nearly pushed its economy into recession.

During a visit to Ukraine in August, Merkel reiterated her opposition to Russia’s annexation of the Crimea, saying it “was in violation to [the] territorial integrity of Europe and if we recognize this principle,” she warned, “than this may happen all over Europe,”

Merkel’s new tone isn’t universally appreciated in Germany. The country — Europe’s largest economy — gets roughly a third of its natural gas from Russia while German exports to the country were worth €36 billion last year. Lobbyists claim up to 300,000 German jobs depend on the trade. German businesses and left-wing politicians, including Merkel’s predecessor, Gerhard Schröder, have cautioned against alienating Russia and sometimes criticized Merkel’s uncompromising rhetoric.

But, as Bloomberg points out, Merkel’s rejection of Ukraine’s proposal to hold a referendum on NATO membership shows the limits of Europe’s support for the country’s incoming government.