Belfast, Northern Ireland ? U.S. Secretary of State Hillary Rodham Clinton said Sunday the Taliban siege of Pakistan’s army headquarters showed extremists are a growing threat in the nuclear-armed American ally, but she contended they don’t pose a risk to the country’s atomic arsenal.

Clinton, in London on the second leg of a five-day tour of Europe and Russia, also joined British Foreign Secretary David Miliband in warning Iran that they would not wait long for the Islamic republic to convince the world that its nuclear intentions are peaceful.

Before stops in Ireland and Northern Ireland, Clinton pledged continued U.S. support for the Northern Irish peace process and said those who continued to exacerbate tension and violence “are out of step and out of time.”