The European Central Bank must remain "cautious" and not rush to lower its key interest rate, Bundesbank President Nagle, the governing council of the European Central Bank, said on Thursday local time. In his speech, Nagle said that the tightening of the labor market and the growth of the economy may delay the sustained return of euro zone inflation to the central bank's 2% target. "It cannot be taken for granted that prices will return to stability in time. Therefore, we need to proceed with caution and must not reduce the policy rate too quickly," he said. The ECB cut its key interest rate in June, and investors expect policymakers to cut it again at their next meeting on September 12. Earlier on Thursday, data released by Germany's statistical office showed that German inflation in August returned to the ECB's target. The German economy contracted in the three months to June, and recent surveys have shown continued weakness.