US Secretary of State Hillary Clinton on Thursday renewed her call on Pakistan to close safe havens for militants, saying the uneasy partner must be "unequivocal" in its approach.

Testifying before Congress after a trip to the region, Clinton said she delivered a "frank" message to Pakistan that it was urgent to act against the extremist Haqqani network, which she blamed for anti-US attacks in Afghanistan.

"I explained that trying to distinguish between so-called good terrorists and bad terrorists is ultimately self-defeating and dangerous," Clinton told the House Foreign Affairs Committee.

"No one who targets innocent civilians of any nationality should be tolerated or protected.

"We look to Pakistan to encourage the Taliban and other insurgents to participate in an Afghan peace process in good faith -- both through unequivocal public statements and by closing off the safe havens," she added.

Clinton used unusually strong language on last week's trip, saying that US tolerance has worn thin after indications that the Haqqani network is targeting Americans, including through a 19-hour siege of the US embassy in Kabul.

The top US diplomat supported the assessment of the outgoing US military chief, Admiral Mike Mullen, who last month said that the Haqqani network was a "veritable arm" of Pakistan's Inter-Services Intelligence.

During Clinton's visit, Pakistan's Foreign Minister Hina Rabbani Khar said that both her country and Afghanistan can do more against militants but denied any official support for the Haqqani network.

Pakistan, once the primary backer of Afghanistan's Taliban regime, switched sides to join the United States in its military campaign after the September 11, 2001 attacks.

But the partnership has been unpopular with the Pakistani public and US officials say that official elements -- perhaps acting outside the control of the civilian government -- have maintained support to militants.