The USA promised Russia that there will be no NATO expansion to the East.
US Secretary of State, James Baker, had agreed with Gorbachev in 1990 in his negotiations on German reunification that there would be no expansion of NATO beyond the then eastern borders of the GDR.
“Baker noted this oral promise in a note: “End result: Unified Ger. anchored* in a changed (polit.) NATO -* whose jurisdiction. would not move* eastwards!”
Recurring pro-Kremlin disinformation that NATO had promised that the Alliance would not expand to the East and that NATO is de facto aggressive.
NATO allies take decisions by consensus and these are recorded. There is no record of any such decision having been taken by NATO or the US. Personal assurances from individual leaders cannot replace Alliance consensus' and do not constitute formal NATO agreements. Moreover, at the time of the alleged promise, the Warsaw Pact still existed. Its members did not agree on its dissolution until 1991. This was confirmed by Mikhail Gorbachev himself in an interview with Russia Beyond the Headlines: