Both countries could benefit from a demotion of the dollar's status on the world stage, according to Aleksandar Tomic, an economist, professor and associate dean at Boston College.
Switching millions of barrels of oil trades from dollars to yuan every day could rattle the Saudi economy, which has a currency, the riyal, pegged to the dollar.
Follow on Twitter The author is a Reuters Breakingviews columnist.
However, now, they are selling oil in U.