NATO Secretary General Jens Stoltenberg hit back on Monday at Russian and Chinese demands for an end to the western defence alliance's expansion amid a stand-off over Ukraine.
"This is an attempt to deny sovereign nations the right to make their own choices enshrined in key international documents," Stoltenberg said at a press conference in Brussels, responding to a joint statement released last week.
The world must "not return to an age of spheres of influence where the big powers can tell others what they can or cannot do so," Stoltenberg said.
Ukraine aspires to join NATO, but is not a member - and therefore not part of the alliance's mutual defence pact. Moscow objects fiercely to its neighbour's membership plans.
A number of eastern European states that were previously part of the Soviet Union have joined NATO since the end of the Cold War in the early 1990s.
Tensions remain high between Russia and the West amid fears that Moscow may be planning to invade Ukraine. Well over 100,000 Russian troops are amassed near Ukraine's borders, according to the NATO chief.
The Kremlin denies any plans to launch an incursion, and in turn accuses NATO of stoking tensions by shifting forces towards the alliance's eastern flank since Russia's 2014 annexation of Crimea.
Russian President Vladimir Putin met Chinese leader Xi Jinping in Beijing on Friday, with the two sides demonstrating their friendship.
China has been supportive of Russia in the crisis so far, and opposes the expansion of military blocs such as NATO.