Deliberate attacks against a country’s economy would probably be handled on a case by case basis through diplomatic channels.

E.g. I’d argue that if China announced it would not repay its massive Treasury debts to the US, that would basically be an act of war even if no aggression was used, just due to the extreme destructive effects. And the reaction would be similarly upsetting, although not quite on the level of an unprovoked, large-scale military action.

But it quickly becomes a discussion of semantics at that point ;)