New Delhi - Manmohan Singh became India's first Sikh prime minister in 2004 when Indian National Congress party chief Sonia Gandhi stunned her supporters by refusing the post and nominated instead her most trusted lieutenant.

A former academic and bureaucrat, Singh, 76, headed a coalition government for five years and is the ruling United Progressive Alliance's prime ministerial candidate in this year's elections.

Widely recognized as the architect of India's economic reforms as finance minister in the early 1990s, Singh now has another major achievement to his credit: a landmark civilian nuclear deal with the United States.

The deal has helped end three decades of nuclear isolation, allowing India to import much-needed fuel and know-how for its nuclear programme.

Singh said he believes India's growing economy needs multiple sources of energy to maintain a rapid growth rate and that an "environment-friendly" source like nuclear energy has a key role to play.

Educated at Cambridge and Oxford universities in Britain, Singh is a highly qualified and experienced economist-technocrat.

He has headed India's Planning Commission and its federal bank, was economic adviser to several prime ministers, was finance minister and has held important positions at international organizations like the International Monetary Fund and the Asian Development Bank.

Born in a village in Punjab province in pre-partition India, Singh does not have a grassroots political base. He is not a crowd-puller and has never won a popular election. He did run once but lost. A member of the upper house of Parliament, or Rajya Sabha, since 1991, Singh is not a candidate in the current elections.

But Singh has the powerful Congress party president's backing, although critics and opposition party leaders have often called the mild-mannered prime minister "weak" and a "puppet" with Gandhi pulling the strings.

On the foreign policy front, Singh has strengthened ties with the United States and continued the peace process with Pakistan although it has stumbled recently after the Mumbai terrorist attacks in November.

Singh's continued economic reform programme has included streamlining taxation and schemes aimed at the development of rural India, where the bulk of the country's people still live, many in strained circumstances.

Singh has waived loans taken by impoverished farmers and promoted one of the world's largest employment-oriented social welfare schemes for rural people. He was instrumental, Congress insiders said, in introducing the right to food in the party's 2009 election manifesto.

In a country where corruption seeps into all levels of government, Singh's biggest asset is his image as a squeaky clean politician and a man of undoubted integrity.

Married to Gursharan Kaur, Singh has three daughters and none of them, so far, unlike the routine Indian politician's family, have showed interest in politics.

A recent opinion poll showed Singh to be one of the top choices for prime minister along with Sonia Gandhi and Hindu nationalist Bharatiya Janata Party leader Lal Krishna Advani.

Singh favours consensual decision making and managed to run a government of often recalcitrant allies for most of five years although he lost the support of leftist parties when he insisted on the nuclear deal with the United States.

A major drawback in recent months has been Singh's poor health. He underwent heart bypass surgery in late January, followed by a six-week convalescence, and is being used sparingly by the Congress party in its election campaign. (dpa)