(AP) - Chairman Ben Bernanke says the Federal Reserve does not have a specific economic target for its new stimulus program and will keep buying bonds until it sees more jobs, lower unemployment and stronger growth. "We are looking for on-going sustained improvement in the labor market," Bernanke said during a news conference Thursday after the Fed announced a series of bold stimulus to get the economy moving. "There's not a specific number in mind. But what we've seen in the last six months isn't it." The Fed said Thursday that it will spend $40 billion a month to buy mortgage bonds for as long as it deems necessary. It plans to keep short-term interest rates at record lows through mid-2015. And it's ready to try other measures if hiring doesn't improve.