At least acording to a document that was shortly published in german "Der Spiegel" such promis to not extend NATO was made. It can be read in this article. The document shows US, UK, French, and German officials discussing a pledge made to Moscow that NATO would not expand to Poland and beyond.
The picture of that document:
Some quotes of important statements which were made during that miting:
"We made it clear to the Soviet Union - in the 2+4 talks, as well as
in other negotiations - that we do not intend to benefit from the
withdrawal of Soviet troops from Eastern Europe," the document quotes
US Assistant Secretary of State for Europe and Canada Raymond Seitz.
"NATO should not expand to the east, either officially or
unofficially," Seitz added.
A British representative also mentions the existence of a "general
agreement" that membership of NATO for eastern European countries is
"We had made it clear during the 2+4 negotiations that we would not
extend NATO beyond the Elbe [sic]," said West German diplomat Juergen
Hrobog. "We could not therefore offer Poland and others membership in