US President Donald Trump has received a rapturous welcome at the start of a visit to India, where he was greeted by the biggest rally crowd of his political career.

Mr Trump and India’s Prime Minister Narendra Modi lavished each other with praise in a reaffirmation of ties between their countries as the pageantry was laid on in spades for the American president.

More than 100,000 people packed into the world’s largest cricket stadium in Ahmedabad, in Mr Modi’s home state.

The event was the pinnacle of the day’s trio of presidential photo opportunities, sandwiched between Trump visits to a former home of independence leader Mohandas Gandhi and a tour of the famed Taj Mahal.

Nearly everyone in the newly constructed stadium sported a white cap with the name of the event, “Namaste, Trump” or “Welcome, Trump”.

Mr Trump opened his speech by declaring that he had come to deliver the message that “America loves India, America respects India and America will always be faithful and loyal friends to the Indian people.”

The exuberant welcome featured musicians on camels and a medley of Bollywood hits and Mr Trump’s campaign rally playlist, featuring numerous Elton John songs that seemed to puzzle most of the crowd.

Even more mystifying was Mr Trump’s attempts to pronounce the names of local cricketing giants Sachin Tendulkar and Virat Kohli.

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None of that got in the way of the boisterous and warm salute received by Mr Trump.

The greeting was a contrast to other foreign trips where massive protests and icy handshakes have stolen the headlines.

In India he was met with a genial embrace from the ideologically aligned and noted hugger Mr Modi.

In Ahmedabad hundreds of billboards featured the president and first lady Melania Trump and thousands lined their motorcade route.

His first stop was Gandhi’s home, where Mr Trump donned a prayer shawl and removed his shoes to inspect the spinning wheel used by the famed pacifist.

Tens of thousands of police officers were on hand to keep security tight and a new wall has come up in front of a slum, apparently to hide it from presidential passers-by.

The cricket stadium was packed with revellers, many of whom sported Trump and Modi masks, as they sat in searing heat. Scores of attendees streamed out before Mr Trump finished his 27-minute speech.

Mr Trump lavished praise on both Modi and the democracy he leads, touting an effort to lift residents out of extreme poverty, saying “India gives hope to all of humanity.”

“The story of the Indian nation is a tale of astounding progress,” Mr Trump said. “Today I say to every Indian, north and south … take pride in the glories of your past. unite for an even brighter future and let our two nations always stand together as powerful defenders of peace and liberty.”

Mr Trump and the first lady also visited the Taj Mahal, the immense white marble mausoleum built in Agra in the 17th century.

Donald Trump is accompanied by wife Melania on a trip to the Taj Mahal. Photo: AP

The visit comes at a crucial moment for Mr Modi, a fellow populist, who has provided over a steep economic downturn and unfulfilled campaign promises about job creation.

The president will conclude his whirlwind visit to India on Tuesday with a day in the capital New Delhi, including meetings with Mr Modi over stalled trade talks and a gala dinner.

The two nations are closely allied, in part to act as a bulwark against the rising influence of China. Mr Trump announced at the stadium that India would soon buy $US3 billion of American military equipment.

Trade tensions between the two countries have escalated since the Trump administration imposed tariffs on steel and aluminium from India. India responded with higher penalties on agricultural goods and restrictions on US medical devices. The US retaliated by removing India from a decades-old preferential trade program.

Alluding to tense trade negotiations, Mr Trump voiced optimism that a deal could be reached but also lightheartedly told the rally crowd about Mr Modi: “Everybody loves him, but I will tell you this. He’s very tough.”

-with AAP