Russia wants NATO to disavow its 2008 promise to one day give Ukraine membership of the U.S.-led military alliance, and for Ukraine to agree to neutrality, Foreign Ministry spokeswoman Maria Zakharova said on Tuesday.

NATO membership for Ukraine is unacceptable for Russia, but a simple refusal to let it join is also now insufficient for Moscow, she said.

"It is worth noting that a refusal to accept Kyiv into NATO is not enough now," Zakharova said in response to a question from Reuters. "The alliance must disavow the Bucharest promises of 2008."

"Otherwise, this problem will continue to poison the atmosphere on the European continent," she said.

Zakharova said that Ukraine needed to return to the position of its 1990 declaration of sovereignty, opens new tab from the Soviet Union, in which Kyiv said that it would become a permanently neutral state, not participate in military blocs and remain nuclear-free.

"What Ukraine needs to do is return to the origins of its own statehood and follow the letter and spirit of the documents," Zakharova said.

"This would be the best guarantee of its security," she said, adding that neither NATO membership nor Western intervention "under the guise of a peacekeeping contingent" could give Ukraine such security.

At a summit in Bucharest in April 2008, NATO declared that both Ukraine and Georgia would join the U.S.-led defence alliance - but gave them no timetable or plan for how to get there.

The declaration was a compromise that papered over cracks between the United States, which wanted to admit both countries, and France and Germany, which feared that would antagonise Russia.

Russia has repeatedly cited the post-Soviet enlargement of NATO, and specifically Kyiv's NATO ambitions, as a reason for the war in Ukraine. NATO rejects that, saying it is a defensive alliance that for the past three years has been helping Kyiv to fight back against Russia's invasion.

President Vladimir Putin says the United States since the end of the Cold War has arrogantly ignored Russia's legitimate concerns about the enlargement of NATO, which was created in 1949 to provide collective security for a group of Western countries against the Soviet Union.

Reuters reported in November that Putin is open to discussing a Ukraine peace deal with Trump but rules out making any major territorial concessions and insists Kyiv abandon ambitions to join NATO.