European stocks are seen opening broadly lower on Wednesday as investors weigh U.S.-Iran tensions and await key U.S. economic data for additional clues on the outlook for U.S. monetary policy. American and Iranian officials are in Qatar, but Iran said it would not meet with top U.S. envoys, raising fresh concerns over the fragile interim ceasefire between the two nations. Renewed exchanges of fire over the weekend have also dampened expectations of a durable truce. U.S. stock futures edged lower as focus shifted to labor market data alongside upcoming remarks from Federal Reserve Chair Kevin Warsh later today at the annual European Central Bank Forum in Sintra, Portugal. The June ADP employment data, due later in the day, and nonfarm payroll figures on Thursday, may provide fresh insights into the Fed's rate path going forward.