US Secretary of State Condoleezza Rice said on Thursday she was convinced that Pakistan was serious about bringing those behind last week's Mumbai terrorist attacks to justice, reported dpa.
She also called on India to show restraint.
"I found the Pakistani leadership very focused and committed to act," she told reporters at a military airbase near the Pakistani capital before ending her brief visit to the country.
Spending just a few hours in Pakistan, she held separate meetings with President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani.
Rice was in Islamabad on the second leg of her South Asian visit as part of diplomatic efforts to defuse escalating tensions between India and Pakistan over last week's terrorist attacks in Mumbai.
During her visit to India a day ago, she was told by the country's leaders they were keeping all options open to deal with the terror threat emanating from Pakistan.
New Delhi has pressed Islamabad to act against Lashkar-e-Taiba, a Pakistan-based militant group which Indian security agencies believed was behind the Mumbai attacks that left more than 170 people dead and over 300 injured.
"What action will be taken by the government will depend on the response we have from the Pakistani authorities," Indian Foreign Minister Pranab Mukherjee said at a joint press conference with Rice on Wednesday.
Pakistan has offered a joint investigation into the incident and action against anyone involved, but warned that in case of a military build-up on its eastern border with India, it would withdraw its more than 100,000 troops fighting Taliban and al-Qaeda militants on its western border.
This would jeopardize the US-led international fight against terrorism in Afghanistan, where many of the attacks are carried out by Taliban and al-Qaeda militants based in Pakistan's tribal region, raising concerns in Washington.
Rice pressed the Pakistani leadership to fully cooperate with New Delhi in investigating the Mumbai carnage and bringing those behind it to justice.
But she ruled out any military response from India.
"This is not a talk about military action. This is a talk about this particular problem which has occurred and which has to be prevented in future," Rice told reporters.
"It is extremely important if something like that has happened, that whatever is done in the process has to be effective to bring people to justice and preventing further attacks, and it doesn't help to do something that might worsen the problem or has unintended consequences," she said.
Rice added that Pakistan itself was a victim of terrorism, in reference to dozens of suicide and otherwise attacks by Taliban insurgents across the country, leaving hundreds of people dead.
Zardari assured Rice that his government "will not only assist in investigations but also take action against any Pakistani elements involved in the attacks.
"Pakistan is determined to ensure that its territory is not used for any act of terrorism," Zardari told US officials, according to a statement from his office.
The US wants Pakistan and India to continue the peace process they launched four years ago to resolve their differences over a number of issues, including the Himalayan region of Kashmir, over which the two countries have fought three wars in the 61 years of their existence.
"I hope they will keep the line of communication open," Rice said. dpa ns yam km im jh