Berlin - In a stunning defeat for German Chancellor Gerhard Schroeder, voters in the country's most populous state dumped his party in a traditional stronghold - forcing him to call for early national elections later this year, 12 months ahead of schedule.

A sombre Schroeder said the drubbing for his Social Democratic Party in the state of North Rhine-Westphalia on Sunday meant he no longer had the national mandate needed to reform the country's struggling economy.

A jubilant Christian Democratic leader, Angela Merkel, celebrated her party's "sensational result" and indicated that she was open to early elections. The opposition plans to choose its challenger on May 30, and Merkel is viewed as the most likely candidate.

Early elections would cut short the second term Schroeder narrowly won in 2002, helped by his opposition to the US-led war in Iraq.

The Social Democrats had held power for 39 years in the western region of 18,1 million people, which includes the industrial Ruhr Valley. But this year, the party faced widespread discontent over surging unemployment - which currently stands at 12,1 percent in the region and 12 percent nationally. - Sapa-AP