WASHINGTON, March 5 (Reuters) - U.S. President Donald Trump told Reuters in a telephone interview on Thursday that the United States will have a role in choosing Iran's next leader. Trump said it was very early in the process of picking a new leader but that Ayatollah Ali Khamenei's son Mojtaba was an unlikely choice."We want to be involved in the process of choosing the person who is going to lead Iran into the future," Trump said.