It's also "bribery" as commonly understood, but I'm not sure it fits the federal bribery statute.
First, a campaign finance charge, if the purpose of the bribery is to influence a federal election. (Given that Biden is leading in the polls, this has some appeal on its face.)
The issue with that charge would be that, as president, Trump has control of our foreign policy apparatus and can make foreign policy decisions on behalf of the United States.