You know synonyms exist right? And "enlargement" and "expansionism" are cleary synonyms in this context.

The background was that President Putin declared in the autumn of 2021, and actually sent a draft treaty that they wanted NATO to sign, to promise no more NATO enlargement. That was what he sent us. And was a pre-condition for not invade Ukraine. Of course we didn't sign that. The opposite happened. He wanted us to sign that promise, never to enlarge NATO.