By Phil Stewart and Steve Holland WASHINGTON (Reuters) -President Joe Biden said on Wednesday he will begin withdrawing U.S. troops from Afghanistan on May 1 to end America’s longest war, rejecting calls for U.S. forces to stay to ensure a peaceful resolution to that country’s internal conflict. In a White House speech, Biden set a goal of withdrawing all 2,500 U.S. troops remaining in Afghanistan by Sept. 11. By pulling out without a clear victory, the United States opens itself to criticism that a withdrawal represents a de facto admission of failure for American military strategy. “It was n…