You are referring to the Bucharest Memorandum, which was not a treaty but just that - a "memorandum" that several countries signed on to. So not "sacred" by any stretch of the imagination.

The memorandum, according to Wikipedia, prohibited the Russian Federation, the United Kingdom and the United States from threatening or using military force or economic coercion against Ukraine, Belarus, and Kazakhstan, "except in self-defence or otherwise in accordance with the Charter of the United Nations."

As you know, the Russians have claimed that their action against Ukraine was done in self defence in accordance with the UN Charter.

That said, what the US and UK have been doing in Ukraine since 2000 could also be described as "economic coercion".

Certainly Biden's admitted threat to withhold a billion dollars in IMF loans unless Ukraine fired their chief prosecutor would amount to economic coercion, but I would say that the $5 billion the US State Department spent on Ukraine leading up to the Maidan Coup was also economic coercion.