However, he called on the international community to exert pressure on Islamabad to bring the 'murderous gangs who perpetrated the horrible crime in Mumbai' to justice.
During the interaction that followed his remarks at the Council on Foreign Relations, a day before his summit with United States President Barack Obama, Dr Singh was asked by president of the CFR Richard Haass, if the 'remarkable restraint' he exercised after 26/11 'was the right decision,' and that if there were a repeat Mumbai-type attack, whether that restraint 'may have come at a cost.'
Singh replied, "There was enormous pressure on me at that time, (but) I resisted that pressure, and I think the decision that I and our government took was on balance, the right decision."
"As regards the future," he said, "I hate to speculate," but hoped that such an 'eventuality does not arise and that's why I believe the world community has an obligation to impress upon Pakistan that it must use all its influence to curb the power of terrorist groups.'
The Prime Minister conceded, "Pakistan has done something to control the activities of the Taliban terrorist groups in federally administered areas, but it is our sincere belief that it is not active as it should have acted in dealing with terrorist elements who are using their energies to target our country."
He complained that 'nor has Pakistan used all its machinery to bring to book all those murderous gangs who perpetrated the horrible crime in Mumbai,' in which nearly 200 Indian civilians were killed as were six Americans and two Canadians.
Thus, Dr Singh said, "Pakistan, in our view, should be pressured by the world community to do much more to bring to book all those people who were responsible for this horrible crime."
"After all," he said, "there is now impeccable evidence that the conspiracy was planned in Pakistan, it was executed with the active connivance of people who are still roaming around freely in Pakistan, and therefore, I respectfully request the world community to use all of its influence on the powers that be to desist from that sort of behavior."
Asked if what happens in Afghanistan would be decisive for Pakistan's future, the Prime Minister said, "There is no doubt in my mind that if the Talibans and the Al Qaeda group of people succeed in Afghanistan, that would have catastrophic results for the security and stability not only of Pakistan, but for the security and stability of whole of South Asia."
"And, please don't forget," he added, "We are talking of nearly 1.8 billion people living in South Asia."
Dr Singh also asserted that such a scenario 'will also affect the course of evolution in the Middle East as well as in Central Asia and maybe, I think, beyond these regions as well.'
Asked if Pakistan, with all of its problems from the economic malaise to domestic terrorism were to fail, and if he's concerned that it could affect India's success to emerge as an emerging power, Singh declared, "We don't want Pakistan to fail."
He said that the 'emergence of democracy in Pakistan is something we welcome. But, at the same time, we have to recognize that there are forces at work in Pakistan -- the terrorist groups that are active and until now they were active only in the federally administered areas along the borders of Afghanistan. Now they, I think, have a grip on several parts of mainland Pakistan."
The Prime Minister warned, "If that process is not controlled, I think it has phenomenal consequences for the security and stability of Pakistan as well as our own security."
On the question of whether he supports a surge in the troop strength of US forces in Afghanistan, since he had arrived in Washington even as President Obama agonizes over such a decision, Dr Singh, who had in the speech he delivered earlier as well as in the question and answer session that followed his speech to the US-India Business Council warned against a premature exit of the US from that war-torn country, said, "I am not an expert on military affairs."
"It would be much too presumptuous on my part to claim that I know what's the right size of troops that ought to be deployed in Afghanistan," he added.
But, Dr Singh argued, "I am quite clear in my mind that Afghanistan requires the sustained support of the global community if it is to return to a path of peace, freedom and an environment in which fundamentalists, terrorist elements, do not have the say of the type that they had some years ago before 9/11."