Obama, David Cameron Discuss National Security Challenges In Iran, Syria, Afghanistan --- WASHINGTON (AP) — President Barack Obama and British Prime Minister David Cameron have discussed ongoing national security challenges in Iran, Syria and Afghanistan. -- The White House said Obama and Cameron spoke by phone Tuesday. The two leaders discussed their support for talks between world leaders and Iran over its nuclear program, a week of talks in Geneva ended without agreement. Talks are to resume next week. - huffingtonpost