FRANKFURT — The euro zone remains vulnerable to shocks because of weak banks and incomplete regulatory safeguards, the International Monetary Fund said Friday, in a warning to European leaders not to slacken their efforts to build a more resilient financial system.

In its first official assessment of the European Union financial system, the I.M.F. urged political leaders to show resolve in addressing the remaining weaknesses in the structure of the euro zone. Unfinished tasks include creation of a mechanism for winding down failed banks, and a system to guarantee customer deposits in order to prevent runs on banks, the I.M.F. said.  Read more