NEW DELHI (AFP) - India, the world's largest democracy, is expected on Wednesday to announce general elections that are forecast to bring the opposition Hindu nationalists led by hardliner Narendra Modi to power.

The election commission is expected to outline the schedule for the polls at a news conference.

The Times of India reported that voting would begin in some states in early April and end more than a month later, with results expected in mid-May.

The world's biggest voting exercise will see about 800 million people trek to the polls stretching from the remote Himalayas in the north to India's tropical southern tip.

It will pit Mr Modi, son of a tea-stall seller, against Mr Rahul Gandhi, the Harvard and Cambridge-educated scion of India's biggest political dynasty.

After two terms of coalition government led by the leftist Congress party, the Bharatiya Janata Party (BJP) under Mr Modi is widely forecast to emerge as the largest party.

Mr Modi, the leader of western Gujarat state since 2001, is seen as a pro-business reformer but his Hindu nationalism and links to anti-Muslim riots worry religious minorities and defenders of India's officially secular character.

The 63-year-old, who rose through grassroots Hindu organisations, is publicly pitching a message of jobs and development to a country struggling with sluggish economic growth and still endemic poverty.

His main opponent in the Congress is the relatively untested Mr Gandhi, the son, grandson and great-grandson of former prime ministers who is leading the party into a national election for the first time.

Opinion polls show Mr Modi, who was chief minister of Gujarat when anti-Muslim riots left as many as 2,000 people dead in 2002, holds a large advantage over his bitter rival.

But whoever emerges as the ultimate victor - and India's opinion polls are notoriously unreliable - will almost certainly have to stitch together a coalition comprising smaller regional parties.

No single party has won a parliamentary majority since 1989 and the electorate has fractured in successive decades, giving often populist regional leaders immense power at the national level.

This would likely limit any "Hindutva" or Hindu nationalist agenda Modi attempts to put forward and could crimp his development plans.

A new movement with national ambitions, the anti-corruption Aam Aadmi (Common Man) Party led by former tax inspector Arvind Kejriwal, will also be an unpredictable element in this year's polls.

Just over a year since its formation, the party won enough seats in December's Delhi state elections to take power in what was seen as a political earthquake in the graft-plagued nation.

CONGRESS ON THE SLIDE

The Congress party under Prime Minister Manmohan Singh and president Sonia Gandhi, the Italian-born mother of Rahul, has seen its fortunes plummet since 2009 when it won a second term in office.

Dogged by corruption scandals and sapped by slow economic growth and high inflation, its focus on new welfare programmes and social spending on the rural poor is unlikely to convince voters to return it to power.

The 81-year-old Singh, one of India's longest-serving prime ministers, will leave office with his formerly stellar reputation based on his work as a reforming finance minister in the 1990s tarnished.

Mr Rahul Gandhi's leadership credentials are also under immense scrutiny as the media-shy 43-year-old who has never held a ministerial post, steps up as the new leader of India's top political dynasty.

India's next government will inherit formidable challenges, with an economy growing at its slowest rate in a decade and the South Asian region entering a crucial period as NATO forces withdraw from Afghanistan later this year.

On foreign policy, a Modi-led government would be expected to take a more hardline stance on neighbouring Pakistan - the BJP has criticised attempts at peace talks by Singh - while he recently warned China over its "expansionist mindset".