India has blamed elements from the banned Pakistani group Lashkar-e-Taiba for the attacks on its financial hub.
Around 10 armed men attacked two luxury hotels and other Mumbai landmarks on November 26, setting off a three-day battle with security forces that left hundreds injured in addition to the fatalities.
Pakistan strenuously denies any governmental connection to the attack and agreed to co-operate with India's investigation, cracking down on a charity it said was linked to Lashkar earlier in the month.
Western political and military figures have kept up pressure on Islamabad to crack down on armed groups such as the Lashkar.
"The media is building up a scenario in which one may get the impression that we are close to war.
"This is not the stage that the two forces are going to go on that sort of alert"
- Assad Durrani, former head of Pakistani intelligence
"It is not threatening talk at all. It is talking facts. We have been assaulted. A terror attack was launched on us. And the perpetrators of that attack were Pakistanis"
- Ravi Sawhney, Indian security analyst
"There have been very threatening statements [from India] saying that they do not rule out military options, and they have been talking about punishing Pakistan.
"So it is obviously natural for Pakistan to heighten its alert levels and be on guard. We cannot let the Indians have a free run and it is a response to what is happening across the borders"
- Brigadier-General Naeem Salik, retired Pakistani military officer
Admiral Mike Mullen, chairman of the US joint chiefs of staff, made a second visit on Tuesday to Pakistan since the attacks.
He "encouraged the Pakistani leaders to use this tragic event as an opportunity to forge more productive ties with India and to seek ways in which both nations can combat the common threat of extremism together", the US embassy in Islamabad said in a statement.
But New Delhi says Islamabad is not doing enough to prevent future attacks.
India's foreign minister, Pranab Mukherjee, said previously that New Delhi would "explore all options" to push Islamabad to crack down on cross-border attacks.
On Tuesday he called on Pakistan to focus on the issues.
"The issue is not creating war hysteria or raising accusing finger against others," Mukherjee said.
"India has requested Pakistan to take action against the perpetrators."
Yousuf Gilani, the Pakistani prime minister, had said on Monday that his country's was ready to fight.
His office quoted him as telling Pakistan's high commissioner to India: "... if war is imposed upon us the whole nation would be united and the armed forces are fully capable of safeguarding and defending the territorial integrity".
India is seeking to build an international support to put pressure on Pakistan, and has received backing from the US and the UN.
Islamabad has complained that, while it agreed to work with India, New Delhi has yet to pass on any evidence indicating Pakistani elements.
While Indian officials insist to the contrary, Ronald Noble, the secretary-general of the world police organisation Interpol, backed Pakistani claims on Tuesday.
Speaking during a visit to Islamabad, Noble said: "What is not acceptable internationally is for information to be put in the media and that information, if it's accurate, not to be placed in police databases."
He said that until Indian authorities pass on details about the suspected attackers, police around the world would be able to do little to identify them.
India gave Pakistan on Monday a letter it says was written by Mohammed Ajmal Kasab, the sole surviving alleged attacker.
In it, Kasab wrote that he and the nine other assailants came from Pakistan. He also requested a meeting with Pakistani envoys, India's foreign ministry said.
But Pakistan has no record of the man in its National Database and Registration Authority, according to the head of Pakistan's interior ministry, Rehman Malik.
Malik said experts were examining the letter, but Pakistan needs more evidence before it can investigate potential links in the country.
In a related development, police in Indian Kashmir announced on Tuesday the arrest of three men accused of plotting a suicide bomb attack.
Kuldeep Khoda, director-general of police in Indian Kashmir, said one, Ghulam Farid, is a Pakistani soldier.
In Pakistan, a military official said Farid was not an active soldier and that he had deserted in June 2006. The official asked not to be named, citing the sensitivity of the matter.