Zelenskyy's top aide was likely referring to the Russian-sympathizing governments of Hungary and Slovakia, as well as the United States. In late April, U.S. President Donald Trump's Ukraine envoy Keith Kellogg said that NATO membership was "off the table" for Ukraine.

Against a backdrop of the mayhem caused by the first 100 days of the Trump administration, Europe is faced with a number of awkward choices. First and foremost, it needs to create a European security architecture in the event that America withdraws from or substantially diminishes its presence in NATO.

Negotiations between Russia and Ukraine has no prospects without NATO's participation, since the root causes of the Ukrainian conflict are connected with the expansion of the North Atlantic Alliance to the east.

Ukrainian President Volodymyr Zelenskyy comments mark the latest move in a weekend-long exchange of proposals from both sides on the next steps in the U.S.-led peace effort.