WASHINGTON—Despite some economic improvements, Federal Reserve Chairman Ben Bernanke warned today it’s still too soon to declare that the budding recovery will last. “We still have some way to go before we can be assured that the recovery will be self sustaining,“ Bernanke said in remarks to the Economic Club of Washington. The Fed chief repeated his belief that the recovery will continue at least into next year. But he cautioned that the economy is confronting some “formidable headwinds”—including a weak job market, cautious consumers and still-tight credit.