NEW DELHI (AFP) - He is a hardline Hindu nationalist who was boycotted by the West for years and has been a vocal critic of "expansionist" China, India's arch-rival.

But Mr Narendra Modi's pro-business record and widespread frustration with the incumbents mean foreign powers are putting their doubts about India's likely next leader to one side for now.

Mr Modi's main opponent when general elections begin on April 7 is Mr Rahul Gandhi, the urbane scion of India's ruling family who was educated at Harvard and Cambridge universities.

But with polls showing Mr Gandhi's party all but certain to lose power to Mr Modi's Bharatiya Janata Party (BJP), analysts say Washington is ready to work with a man regarded as persona non grata until a few weeks back.

"The US wants to be very practical. Essentially, it sees Modi as a very probable next prime minister of India and the US-India relationship is too important for Washington to be, really, hijacked by this problematic visa issue," said Mr Michael Kugelman, a South Asia expert at Washington's Woodrow Wilson International Center for Scholars.

Mr Modi, 63, chief minister of Gujarat, was placed on a visa blacklist by the US and European governments following communal riots on his patch in 2002.

More than a thousand people were killed, mostly Muslims.

European countries began lifting their boycotts in late 2012 as it became clear Mr Modi could be his Hindu nationalist party's candidate for premier.

But he continued to be cold-shouldered by the US until last month when Ambassador Nancy Powell met him in Gujarat.

Observers say policy-makers, rattled by a recent bust-up over the arrest of an Indian diplomat in New York, want to prevent a Modi victory from sparking new tensions between the world's two largest democracies.

"People in this town (Washington) are essentially ready to move to the next phase which is to try to get the US-India relationship back on track, which of course had been hit pretty hard over the past few months," said Mr Kugelman.

Mr Lalit Mansingh, a former Indian ambassador to the US, said there was no real warmth but Washington and Mr Modi's camp realise they need to work together.

Mr Mansingh said Mr Modi regards good ties with Washington as key to firing up India's economy after growth slowed to its lowest rate in a decade - regardless of any slight he might feel over his past treatment.

"It is not a sign of warming up, it is a sign of normalising," Mr Mansingh said.

"If he is pro-business, the US can't be ignored, principally because of our own economic downturn."

Under Mr Modi, Gujarat has gained a reputation for attracting foreign firms - such as US auto giants Ford and Chevrolet, which have factories there.

In contrast, many US firms have grown disillusioned with trying to do business in India over the past 10 years of Congress rule, as they try to navigate a maze of taxation and red tape.

Congress is putting its faith in Gandhi to extend its rule.

But the 43-year-old - once described as an "empty suit" in a leaked US diplomatic cable - has never held office and has had little to say about foreign policy or trade on the campaign trail.

In a recent speech to businessmen, Mr Modi pledged to foster a more investor-friendly environment and emphasised that "trade and commerce need to be brought to the centre" of Indian foreign policy.

Mr Ron Somers, president of the United States-India Business Council, said American businesses had been impressed by Mr Modi's stewardship of Gujarat and welcomed the decision to bring him in from the cold.

"That is why it was so important for the US government to catch up to the US business community, which is bullish on Gujarat," Mr Somers said.

The same belief in the importance of trade is also likely to drive Modi's attitude towards Beijing, say observers.

During a recent rally in Arunachal Pradesh, one of the theatres of a brief but bloody war with China in 1962, Mr Modi raised eyebrows when he told Beijing to shed its "expansionist mindset" and not to think about "snatching" the territory from India.

His comments reinforced Mr Modi's reputation as a nationalist who will not be cowed by India's giant neighbour after accusations that Congress has been too passive in recent border spats.

But Mr Modi has also been a frequent visitor to China, seeking investment for Gujarat and voicing his admiration for its economic performance.

Mr Srikanth Kondapalli, a China expert at Delhi's Jawaharlal Nehru University, predicted Modi would work with Beijing to stoke trade rather than antagonise it with nationalist outbursts.

"Modi's focus is on economic growth. If he has to galvanise opinion in his favour he has to resurrect economic growth," he said.

Indeed, Beijing took care not to rise to the Arunachal Pradesh speech, with an opinion piece in the state-run Global Times saying there was "no need to exaggerate the significance of Modi's remarks".

For all the willingness of foreign governments not to prejudge Mr Modi, advocacy groups say it is important they make clear their concerns about human rights in the light of the 2002 bloodshed.

"They should... encourage him to send a strong message to his supporters that such actions, whether targeting of minority communities or subsequently covering up the crime, will not to be tolerated," Mr Meenakshi Ganguly, South Asia director of Human Rights Watch, said.