WASHINGTON (Reuters) - Republicans’ tax plan would not make adjustments retroactive, White House economic adviser Gary Cohn said on Friday, despite calls from U.S. lawmakers who want cuts to apply to 2017 as the party aims to pass the bill by year’s end. “We’re trying to deliver great tax reform to the American public. We can’t get it retroactive to this year. We’re trying to do a tax plan that starts on Jan. 1 of next year,” Cohn said in an interview with Fox Business Network. (This version of the story was refiled to correct the headline to make it “Fox Business Network” instead of “Fox Business News”) 