POTUS might start with a somewhat non-official - but close to the Chinese ruling power - go-between (cut out) to establish an unofficial avenue of communication. Lay some of his evidence cards on the table and let them respond. If in the exchanges China accuses the USA ask them to show their proof. If any American is implicated then prosecute them... back and forth, but not at such an official level that forceful response might be required.
Just an idea to avoid fast escalation. It has been done before.
Nice idea.
Are/were you a diplomat?
Sec of Defense An infantry battalian 1600 troops are moving into DC now
Democrats Chickens Come Home to Roost
Townhall.com ^ | June 2, 2020 | Derek Hunter
https://www.freerepublic.com/focus/news/3850967/posts?page=1