KAUNUS, Lithuania (Reuters) - German Defense Minister Ursula von der Leyen will meet U.S. Defense Secretary Jim Mattis in Washington on Friday, a ministry spokesman said. Her visit comes ahead of a meeting of NATO defense ministers next week and the Munich Security Conference a week later. Mattis has sought to reassure NATO allies like Germany that the United States remains committed to the alliance despite comments by President Donald Trump that it is obsolete because it failed to protect Europe against Islamist attacks. 