WASHINGTON (Reuters) - U.S. President Donald Trump said on Friday he focused on humanitarian aid for Venezuelans during a phone call with Russian President Vladimir Putin, backing away from his administration's recent harsh rhetoric about Russian involvement in the crisis. In a rare call, Trump and Putin spoke for more than an hour, their first known conversation since December and since tensions flared in Venezuela, where Washington backs opposition leader Juan Guaido and Moscow supports President Nicolas Maduro.