WASHINGTON (Reuters) -Elon Musk said on Friday his rocket company SpaceX cannot indefinitely fund its Starlink internet service in Ukraine, which has helped the country’s civilians and military stay online during the war with Russia. Musk’s comment on Twitter came after a media report that SpaceX had asked the Pentagon to pay for the donations of Starlink. The billionaire has been in online fights with Ukrainian officials over a peace plan he put forward which Ukraine says is too generous to Russia. A senior defense official told reporters on Friday that the U.S. Department of Defense would no…