BELFAST, Northern Ireland (AP) - 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."

With her British counterpart, Clinton said there was nothing to suggest that Pakistan’s nuclear weapons could fall into terrorist hands despite Saturday’s audacious Taliban attack on the army headquarters in Rawalpindi that highlighted security weaknesses.

Clinton said extremists were "increasingly threatening the authority of the state, but we see no evidence that they are going to take over the state. We have confidence in the Pakistani government and military’s control over nuclear weapons."

Miliband told reporters at a joint news conference with Clinton that although Pakistan faced a "mortal threat" from extremists, there was no danger of its nuclear weapons being compromised.

He scolded those who might raise the suggestion. "I think it’s very important that alarmist talk is not allowed to gather pace," he said.