Kerry: 'Do what we must' to stop Iran on nukes Associated Press Copyright 2013 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Updated 11:08 am, Thursday, January 24, 2013 WASHINGTON (AP) — Sen. John Kerry, President Barack Obama's nominee for secretary of state, said Thursday that the United States will "do what we must" to prevent Iran from developing a nuclear weapon even as he signaled that diplomacy remains a viable option with Tehran. Testifying at his confirmation hearing, and with Senate approval a foregone conclusion, Kerry addressed a range of concerns raised by members of the Foreign Relations Committee, from his past outreach to Syrian President Bashar Assad to GOP concerns about the nomination of Republican former Sen.