WASHINGTON (Reuters) - U.S. Democratic presidential candidate Bernie Sanders expressed disappointment on Friday after Republican presidential candidate Donald Trump said he would not debate Sanders ahead of California’s June 7 primary. “I heard that he was going to debate me, then I heard that he was not going to debate me, then I heard that he was going to debate me. Now you’re telling me that he is not going to debate me. Well, you know, I hope that he changes his mind again,” Sanders said in a video clip posted on an ABC News Twitter account. 