Russia has called for "a 100% guarantee that no-one would think about Ukraine joining Nato", President Vladimir Putin's spokesman has told the BBC, reports GHN.
Dmitri Peskov added that Nato's gradual approach towards Russia's borders had made Moscow "nervous".
Earlier, Mr Putin said the US would never "subdue" Russia over Ukraine.
Germany's foreign minister said Europe was heading for "confrontation instead of cooperation", amid warnings of a Russian build-up on Ukraine's border.
During a joint news conference in Moscow with Russian Foreign Minister Sergei Lavrov, Frank-Walter Steinmeier said that as fighting escalated in east Ukraine he could see "no grounds for optimism".
The minister also urged Russia to abide by the Minsk ceasefire agreement.