While the euro crisis is the most immediate concern, she also warned that the U.S. economy could fall of a "fiscal cliff" if the nation's debt is not put on a sustainable path.

"European banks are at the epicenter of our current worries and naturally should be the priority for repair," she said. "But this does not mean we should overlook the broader implications of today's interconnected world."

Lagarde pointed to the recent disclosure by JPMorgan Chase that the largest U.S. bank by assets had lost at lest $2 billion on risky trades.

"There are still many questions surrounding JPMorgan's trading loss. Yet, they should be seen as a warning shot over the bow," she said. "It reveals that too much risk remains."