US Secretary of State Hillary Clinton wants Pakistan to do more to check extremists with a veiled warning of the consequences of a terrorist attack that can be traced back to that country.

"We think that there's more that has to be done," she said Thursday at an interaction at the US Institute of Peace, a Washington-based think tank when asked to clarify her remarks about her earlier warning of "severe consequences" in such as an event.

"And we do fear the consequences of a successful attack that can be traced back to Pakistan, because we value a more comprehensive relationship. So we do expect more," Clinton said repeating her warning given an interview with CBS Sunday, though in an indirect manner.