By Nandita Bose and Jeff Mason WASHINGTON (Reuters) -President Joe Biden will announce an additional $800 million in security assistance to Ukraine on Wednesday, but his position on a “no-fly zone” has not changed after Ukrainian President Volodymyr Zelenskiy’s urgent appeal to the U.S. Congress for military help to fend off a Russian invasion, the White House says. Biden will address Zelenskiy’s remarks in his planned speech, a White House official said. He also plans to detail funding to come from a massive spending bill Biden signed into law that includes $13.6 billion in new aid to Ukraine…