MANMOHAN Singh is an unlikely revolutionary. Yet as the leader of 1.1 billion people, the world's largest democracy and its second-largest nation, the Indian Prime Minister has already enacted three profound revolutions.

As finance minister during the 1991 economic crisis, Singh decisively turned India towards market liberalisation. Then after the last election he became India's first non-Hindu prime minister -- he is a Sikh -- showing the depth of India's secular democracy.

Now, in the nuclear co-operation agreement he has struck with US President George W. Bush, Singh may have marked India's decisive emergence as a global power.

The nuclear deal is important in itself, but its true significance is as a marker of a new power structure in Asia and the world. A near trillion-dollar economy growing at 8 per cent a year, India in a couple of decades will overtake China as the world's most populous nation.

Bush hailed New Delhi last week as a global power and took every step he could to cement a US-India partnership, in trade, economics, politics, defence co-operation, nuclear technology, the war on terror and the promotion of democracy.

While John Howard will operate on a more modest scale this week, the Prime Minister, too, seems to "get" India and understand the profound challenge it poses for Australian policy.

I met Singh at the weekend at his official New Delhi residence. This is a modest single-storey white building, dating from the time of the architect Lutyens, who designed New Delhi as a magnificent capital.

It is certainly infinitely more modest than the imperial Zhongnanhai Palace in Beijing occupied by China's rulers.

Singh received me in a small, elegant sitting room. In his fine blue turban, proud white Sikh beard and traditional Indian garb, Singh has a bearing both regal and down to earth.

His voice has the soft timbre of the Cambridge don but the words are crisp and direct, with the addition of the traditional mellifluous Indian influence.

Singh always resists casting himself in historic mode, but says of the India-US agreement: "We are too close to the events, I think, to recognise in full measure the importance of this agreement.

"If this process we have started goes through, and the international community in its wisdom dismantles various restrictive regimes which it has erected to prevent the transfer of high technology to India, it will have tremendous significance for India's development.

"We draw on shared values of democracy, rule of law, pluralism and fundamental freedoms." he says. "The US-India relationship today is better than it has ever been before."

Singh has never visited Australia but he has met Howard twice for bilateral discussions at ASEAN meetings. He made many Australian friends during his time at Cambridge, where he was a brilliant economist. He recalls with particular fondness the contribution of Sir John Crawford, whom he calls "a great son of Australia and a great friend of mine", to the green revolution that helped India feed itself. As an adviser to the World Bank, Crawford would visit India every year.

Singh wants the Howard visit to propel the Australia-India relationship dramatically forward. He wants both sides to overcome the prejudices of the past, saying the relationship has been greatly underdeveloped until recently.

"Part of it was the result of the Cold War, because in the Cold War we were on different sides. There was (Indian) distrust of Australia, and there was distrust of India in Australia, and I do believe we have a lot to co-operate in."

Singh nominated regional institutions as part of this co-operation. Both India and Australia joined the East Asia summit last year, and India strongly backed Australia's inclusion, which was important to the ultimate outcome.

Although Singh did not mention APEC, it is a longstanding Indian position that it would like to join APEC, which Australia hosts in Sydney next year.

More than any other individual, Singh is responsible for India's booming economy today.

Though formed in an intellectual tradition favouring heavy state intervention in the economy, he saw the need to switch to a market-based approach.

"I believe we are inching towards a sustained increase of 7 to 8 per cent per annum in our economy, maybe a bit more in the next five or six years.

"This much growth I believe is now built into our economic and political processes. That does not mean the economy is on auto-pilot. We need to do a lot more to improve our physical infrastructure and our social infrastructure, particularly to ensure the poorer sections of our community get adequate opportunities to become participants in social and economic development."

There is substantial criticism of Singh's government that it has slowed the pace of economic reform. Somewhat to my surprise, he doesn't duck this criticism. "Yes and no. In one sense yes, we are a coalition government and our partners on the Left do not always share our view of what should be the orientation of economic policy. So in one sense, yes we could move at a much faster pace than we are moving.

"But the direction of the change is towards increased liberalisation and greater opening of the Indian economy, and giving a greater role to private enterprise in the management of the economy. That has come to stay.

"Nobody is questioning that. There are differences about the pace of reform and how much space we should give to foreign investment, but no one today is wanting to go back to the old licence raj, as we used to call it."

Singh has the bald figures on his side. The Indian economy grew by better than 8 per cent in 2004, better than 7 per cent last year, and will grow at better than 8 per cent again this year. It is the second-fastest growing substantial economy in the world, after China.

A prime minister of India is always beset with security challenges, especially of Islamist terrorism originating in Kashmir, and, many Indians believe, in Pakistan. I asked Singh whether he believes Pakistan is still sponsoring terrorism, in India and more widely.

He would not use precisely those words, but the implication of the words he did use is clear enough: "We feel Pakistan has to do a lot more to prevent the use of Pakistani territory for terrorist acts directed at our country.

"I very much hope that Mr Howard will convey this same message (to the Pakistanis). Terrorism as an instrument of state policy is not acceptable to the civilised world, least of all after 9/11. Terrorism is hurting Pakistan as well. We see it every day."

The genius of democracy across the world produces many remarkable leaders -- none more so than Manmohan Singh.