Europe's reluctance to compromise on its energy supplies has, for now, taken one of the most impactful measures off the list of international sanctions against Russia over its invasion of Ukraine: ouster from SWIFT, the dominant messaging system behind global payments.

U.S. President Joe Biden says it's still an option, and the U.K. and some other countries in Europe—Poland and Lithuania, for example—are pushing hard for its inclusion.

But two key factors are holding things back: Pushback from countries like Germany and Italy over energy security and worries it could invigorate rival messaging systems, including one from China or another that Russia started in 2014 after being isolated over the annexation of Crimea.