Berlin (dpa) - The leader of Germany‘s Social Democrats (SPD), Martin Schulz, called on his party to uphold its national responsibility and to strengthen Europe by backing talks with Chancellor Angela Merkel‘s conservatives to build a new government."A strong SPD is necessary to make Germany strong, and a strong Germany is necessary to make Europe strong," Schulz told a party congress. "We must not govern at any price," Schulz said, adding that what was decisive for the SPD playing any role in a new Merkel-led government is that the party can implement its programme.He said the renewal of the SPD cannot be placed above the interests of the nation.