European finance chiefs begin the final stage of hammering out a Greek rescue to prevent the euro area's first sovereign default after the country was slapped with the world's lowest credit rating by Standard & Poor's.

Yields on 10-year Greek bonds climbed to a euro-era record of 17.12 percent today before an emergency session of finance ministers in Brussels. They're seeking to narrow differences on how investors share the cost of easing Europe's biggest debt burden and to wrap up a new financing plan at a leaders' summit on June 23-24, a year after Greece received a first bailout.

“The market is placing much too high a probability on this possibility that Greece will default imminently,” Peter Westaway, chief European economist at Nomura International Plc, said today on Bloomberg Television's “First Look.” “Policy makers just aren't going to let Greece default. It's completely fanciful to think this is going to happen.”