India's government handed over "evidence" on the Mumbai attacks to Pakistan on Monday, saying it expected a prompt investigation as New Delhi tried to pile on diplomatic pressure on its nuclear-armed rival.
"It is our expectation that the Government of Pakistan will promptly undertake further investigations in Pakistan and share the results with us so as to bring the perpetrators to justice."
When Pakistani Foreign Minister Shah Mehmood Qureshi was asked on Monday whether he expected U.S. pressure, he replied.
"We are friends and friends respond to understanding not pressure. Pressure never works."
India has blamed Pakistani gunmen for the November attacks in Mumbai by 10 gunmen that killed 179 people. The rampage through India's financial hub has revived hostilities between the neighbours that have fought three wars since 1947.
Pakistan denied any state involvement in the attack.
"The material is linked to elements in Pakistan," the foreign ministry said in a statement.
This is the first time India has handed over evidence regarding the Mumbai attacks to Pakistan.
The "evidence" presented to Pakistan included a confession from the one surviving gunman, details of communications links with "elements in Pakistan", and data retrieved from GPS and satellite phones, the ministry said.
"It is our duty, my duty to examine the dossier carefully, understand it and be truthful to myself, to my country and the neighbourhood," Qureshi told Reuters.
On Monday, U.S. Assistant Secretary of State Richard Boucher was in Islamabad for meetings with government leaders on various issues, including the Mumbai attacks, a U.S. embassy spokesman said.
India says that so far it has not been satisfied by Pakistan's response. New Delhi wants Islamabad to dismantle what it says are terrorist training camps on its territory, and extradite 40 suspects.
Pakistan says it will act if India provides proof, although many Indians suspect Pakistan will do the very minimum needed to fend off international pressure.
Some Indian officials claim that there was Pakistani state involvement in the attack.
Home Minister Palaniappan Chidambaram claimed on Sunday that Mumbai attacks pointed to the involvement of "state actors" in Pakistan, hinting at a role for Pakistan's military spy agency, the ISI.
Qureshi said on Monday that Chidambaram's statement was "speculation".
"I think that Pakistan has led itself to believe that the U.S. and NATO allies need Pakistan so much that there is precious little the United States will do," said G. Parthasarathy, a former ambassador to Pakistan.
India's diplomatic approach will be severely tested if Pakistan is perceived by New Delhi as stonewalling the investigations, or if there is another attack.