Aug 17 (Reuters) - Minneapolis Federal Reserve President Neel Kashkari on Tuesday said he still sees "a lot of slack" in the U.S. labor market, with some six million to eight million Americans out of work who would have been employed had the pandemic not hit. "There still is slack on the sidelines," said Kashkari at the Pacific Northwest Economic Regional Annual Summit in Big Sky, Montana. He said that recent high inflation readings are likely to be short-lived, and should subside as workers return to the labor force; still, he added, the Delta variant could slow the recovery.