Ullman, a senior associate at the Centre for Strategic and International Studies, where he heads its political-military and strategy programmes, is currently in Islamabad, where he has been meeting senior government officials.
"There was absolutely no ISI involvement at the senior levels," Ullman asserted in an interview with rediff.com
"This is something that the ISI would have wanted to prevent," he argued, and reiterated, "There was no direct ISI involvement whatsoever."
Ullman acknowledged, "For the time being, one cannot preclude the possibility that the junior level or residual members of the ISI or a former staffer of the agency might have played a role."
He claimed that the ISI, "has changed completely and I think that it is a different organisation, because I've had the chance to interact with the agency."
Ullman, a product of the US Naval Academy, who has participated in more than 150 combat missions and patrols in Vietnam and later commanded a destroyer in the Persian Gulf, defended the spy agency.
"I appreciate the pressure under which Pakistan and the ISI are both operating, because the circumstances have changed, even on the Kashmir issue."
"The issue of Kashmir is very important for Pakistan and Afghanistan, but it is not in Pakistan's interest any longer to be using these groups (like the Lashkar-e-Tayiba) pro-actively because these groups, in many cases, have turned against Pakistan," he said.
Ullman, who also serves as a distinguished senior fellow at the National Defence University, pointed out, "They had created a Frankenstein monster initially -- to deal with Kashmir and the Soviets in Afghanistan -- and now that monster has metastasised into something that's after Pakistan and the Pakistanis understand that."
He termed India's insistence on ISI's involvement in the Mumbai attacks as incorrect and based on "past history, which is wrong."
Ullman is also an adviser to senior US government officials and is credited as being the principal author of the 'shock and awe' doctrine.
Speaking on the steps that can be taken in the wake of the deadly attacks, Ullman said, "There has to be a thorough, cooperative, coordinated and transparent investigation."
"There is no doubt in my mind that Pakistanis were involved -- the evidence there is irrefutable. But Indians and other people were involved as well," he said.
Of the 19 hijackers involved in the 9/11 attacks, 17 were Saudis, "The United States could have said, 'We are going to war with Saudi Arabia.' That's absurd. So you need an investigation," he explained.
"Both sides have got to realise that they are threatened by very serious insurgencies -- the Pakistanis do, the Indians do not," he said.
According to him, US Secretary of State Condoleezza Rice and Admiral Michael Mullen, chairman of the Joint Chiefs of Staff, should have asked India to take action against insurgents during their India visit. "But when they came to Islamabad, they said very strongly that Pakistan must go after the insurgencies in Pakistan, which Pakistan is doing," he pointed out.
"India must take care of its insurgencies, which in some ways are just as bad and possibly even worse than the ones in Pakistan," he added.
Ullman conceded that the attack on Mumbai had been conspired, planned and launched from Pakistan, but was quick to add, "If India does not cope with its insurgencies, these attacks are going to start again. Even if they emanate from inside India, the initial tendency will be to blame Pakistan, even though it might not be involved."
The security expert stressed "complete sharing of information and anti-terrorism cooperation" and predicted, "You are going to see a continuing operation against the militant groups in Pakistan by the authorities."
The operation, he says, will be taken over by the interior ministry, which "will deal with these groups."
Ullman believes that India should hand over the evidence collated in the Mumbai attacks to Pakistan as "there is no way these people (arrested by the Pakistani authorities) can be convicted."
He compared this with the case of a mafia gangster, "who everybody knows is guilty of something, but nobody will come forward with evidence or proof. Since much of the evidence is classified intelligence, it may be very difficult to take that into a court of law in order to get a conviction."
Ullman defended Pakistan's refusal to hand over the arrested terrorists to India. "Even if these people were turned over to India, what can India do to them without violating their human rights if India has no evidence in court?" he added.
Once again bringing up the analogy of 9/11, Ullman said, "It is rather like these 9/11 hijackers and the group that planned it. It should make no difference to the United States where these people are brought to justice. It should be that they have been brought to justice --that should be the issue."
"India would like to have -- if not some revenge -- certainly some solace in trying these people. But as long as they are brought to justice, that should be satisfactory," he says.
He argued that "Indians have to realise and Pakistanis have to realise that in these kinds of cases -- there has to be legally accepted and justifiable proof for a conviction."
Ullman refuted reports about being an informal adviser during Barack Obama's campaign and a key player advocating Pakistan's cause in the president-elect's team. "I am a fierce political independent," he clarified.