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BBCSecretary of State Hillary Clinton has warned Pakistan of unspecified "severe consequences" if it can be linked to a successful extremist attack on the US.
She told CBS while Pakistan had become more helpful in tackling extremists, co-operation could still be improved.
A Pakistani-born US citizen has been charged with the attempted bombing in Times Square in New York a week ago.
Earlier, Defence Secretary Robert Gates said the US was prepared to increase military assistance to Pakistan.
"We're willing to do as much... as they are willing to accept," he told reporters. "We are prepared to do training, and exercise with them. How big that operation becomes is really up to them."
But he played down the chances of an extended crackdown on militants, saying Pakistani forces were already "thinly stretched".
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http://news.bbc.co.uk/2/hi/americas/8669512.stm