The US administration has asked Pakistan to ensure that those responsible for the Mumbai terror attacks are punished inside the country instead of being extradited to India, according to a media report.

The Bush administration has informed the Pakistan government that it would like it to initiate 'prosecution with sufficient efforts to ensure conviction' of those behind the Mumbai incident, the Dawn newspaper quoted US sources as saying.

The move is a 'clear change' in the attitude of the US, which earlier had backed the Indian demand that some of the suspects be extradited to India.

The change apparently has been noticed in New Delhi [Images], where External Affairs Minister Pranab Mukherjee [Images] said on Thursday that the US pressure on Pakistan to act against the Mumbai perpetrators had 'not produced tangible returns', the newspaper said.

US officials had earlier supported India's demand for the handing over of those behind the attacks but the change in their attitude followed a realisation in Washington that it would not be easy for the Pakistan government to extradite key Lashker-e-Tayiba leaders to India, the sources said.

In their negotiations with US officials on this issue, the Pakistanis insisted that the extradition of Pakistani citizens to India -- particularly when the two countries did not have an extradition treaty -- would have unpredictable consequences for the government, the sources said.

'The Pakistanis argued that the resulting political instability would not only weaken the government but could also harm the war against the Taliban [Images] and Al Qaeda [Images] militants in Afghanistan as Pakistan played a key supporting role in this war,' the report said.

The 'softening in US attitude' is also linked to a crackdown in Pakistan on LeT and other militant groups. The move appears to have convinced the US that Pakistan is serious about uprooting militant groups that use its territory for conducting attacks inside India and Afghanistan, the report said.

The Americans, who have stayed involved with the investigation, have 'noted with satisfaction that Pakistani authorities were seriously interrogating the suspects involved in the Mumbai attacks and looked determined to find out those responsible'.

The New York Times had on Thursday reported that Pakistani authorities had obtained confessions from LeT members that they were involved in the Mumbai carnage. The Times quoted a Pakistani official as saying that the 'most talkative' of the LeT leaders being interrogated is Zarar Shah, the group's communications chief.

The Wall Street Journal had on Wednesday reported the news of Shah's confession. The Times reported LeT operations commander Zakiur Rehman Lakhvi is also cooperating with investigators.

Mukherjee too said that an FBI team currently in Pakistan had shared with Pakistani authorities 'strong evidence' of Lashker-e-Tayiba's involvement in the Mumbai attacks that killed over 180 people.

He said an extradition treaty is not needed for handing over three terror suspects Dawood Ibrahim [Images], Jaish-e-Mohammad chief Maulana Masood Azhar and Lakhwi, who India believes staged the Mumbai attacks.