An employee of German car manufacturer Adam Opel AG blows a whistle as he attends a demonstration ahead of a warning strike in front of the Opel headquarter in Ruesselsheim near Frankfurt May 3, 2007. Workers in Germany's engineering and metalworking sector aim to begin work stoppages after unions failed to agree with employers to raise wages by 6.5 percent. REUTERS/Kai Pfaffenbach(GERMANY)