By Doina Chiacu and Susan Heavey WASHINGTON (Reuters) -The U.S. baby formula shortage should improve dramatically in coming weeks, President Joe Biden and top officials said on Friday as the administration scrambled to reverse a shortfall that hits lower-income Americans particularly hard. The United States is working with manufacturers to allow more importation of baby formula, Biden told reporters in the Rose Garden. “We’re going to be, in a matter of weeks or less, getting significantly more formula on shelves,” he said. Food and Drug Administration Commissioner Dr. Robert Califf said earli…