It could be the International Monetary Fund's SDR (Special Drawing Rights) which consist of a basket of currencies including the dollar but even our friends are not going to put up with the loss of sovereignty inherant in our ability to confiscate their financial holdings in dollars any time we wish. Our harsh Sanctions re: Russia have forced them to rethink how they hold their financial assets and many are considering dollar alternatives as we speak.
Additionally, the Chinese are ready to introduce a Gold backed Yuan to compete with our Fiat Dollar (backed by nothing except our pomise to print more if we need to). No one has ever printed their way to Prosperity. If that were possible Zimbabwe and Venezuela would be the Garden spots of the World and they have been forced to eat their pets in both countries after trying to do so.