US Secretary of State Condoleezza Rice made an unannounced trip to Pakistan on Thursday to urge the Pakistani government to take a 'tough line' on terrorism in the wake of last week's militant attacks on Mumbai.

'The global threat of extremism and terrorism has to be met by all states, taking a very tough and hard line, and so that is what I am going to discuss,' Rice told reporters travelling with her from New Delhi to Islamabad.

'Pakistan has to determine its own response here. It just needs to be a robust response and it needs to be effective,' she said.

India has blamed groups based on Pakistani territory for the attack by a band of gunmen which killed nearly 200 people, including six Americans, in the country's financial capital.

Rice was going to meet army chief General Ashfaq Kayani first at army headquarters in Rawalpindi, before holding talks with President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani, the leaders of an eight-month-old civilian government.

She said she was not acting as a go-between with New Delhi, and said the onus was on the Pakistani leadership 'as a whole' to tackle the threat of terrorism.

'I am going there to talk about a Pakistani response, not to carry messages,' she said. 'This is not a matter of the international community somehow in juxtaposition, or against, the Pakistani government.'    

Rice's visit to Islamabad followed one by the chairman of the US Joint Chiefs of Staff, Admiral Mike Mullen, on Wednesday. America's top military officer urged Pakistan to investigate all possible links between the Mumbai attacks.

In a thinly veiled reference to the Kashmir-focussed militants suspected of carrying out the attack on Mumbai, Mullen also encouraged Pakistan to act against jihadi groups everywhere, not just in regions bordering Afghanistan, where Pakistani security forces have been fighting tribal militants, the Taliban and al Qaeda.

Rice met Mullen for breakfast in New Delhi, to hear his impressions from meetings with Pakistani officials. 'He really, I think, got a sense of the commitment of the Pakistani government to the public messages that they have been issuing,' Rice said.

Pakistan has condemned the assault, denied any involvement by state agencies and vowed to work with India in the investigation.

A confrontation between the South Asian rivals would undermine US-led efforts to bring stability to Afghanistan and defeat al Qaeda.

Pakistani security officials have said they could feel forced to abandon the campaign against militancy and take forces away from the Afghan border, where they are fighting al Qaeda and the Taliban, and move them to the Indian border if tension increases.-Reuters