Outside the 17-country euro zone, numerous European central banks are eyeing defensive measures to protect against the possible fallout if the euro zone were to unravel, other people said. Several, including Switzerland, are considering possible replacements for the euro as the external reference point, or peg, they use to try to keep their currencies‘ values stable.

The central banks‘ planning is preliminary, according to the people familiar with the matter. It doesn‘t represent an expectation that the euro zone is headed for dissolution.