US President Barack Obama begins a trade-focused visit to India on Saturday in Mumbai with tribute to the victims of the 2008 attacks on the city by Islamic extremists.

India's financial hub is Obama's first stop on a four-nation Asia tour, which is expected to be heavily weighted towards strengthening ties with fast-growing economies in the thriving region.

The trip comes just days after his Democratic Party's drubbing in mid-term elections in which the state of the US economy was a primary source of voter dissatisfaction.

The visit to Mumbai will see Obama and his wife Michelle become the most high-profile guests to stay at the Taj Mahal Palace hotel since the attacks two years ago by 10 Islamist militants that claimed 166 lives.

Obama is expected to meet survivors and pay tribute to those who died at a permanent memorial erected at the luxury seafront hotel, which was the focus of the militant assault and where 31 people, including 12 members of staff, were killed.

Security is tight for the visit, with roads closed, a ban enforced on sea traffic off the coast, and the plaza near the Taj and Gateway of India monument sealed off.

Some 5,000 security personnel, including US Secret Service, Indian intelligence officials and elite commandos have been deployed around the venues for the presidential visit in south Mumbai.

At the time of the attacks — likened by some in India to those in the United States on September 11, 2001 — the then president-elect Obama said they demonstrated "the grave and urgent threat of terrorism".

He also called for closer ties with India and other countries to root out and destroy extremist networks. US officials now say that cooperation with India on counter-terrorism is at its highest-ever level, despite India's misgivings about continued US support for its longstanding rival and neighbour Pakistan.

The only surviving gunman from the attacks said they were recruited, trained and equipped by the banned, Pakistan-based Islamist group Lashkar-e-Tayyaba (LeT) with support from elements in the country's military and intelligence service.

New Delhi has also questioned how much the United States knew about the activities of a US-Pakistani national, David Coleman Headley, who earlier in 2010 admitted scouting potential targets in Mumbai before the attacks.

In Mumbai, Obama will visit the house where the father of the Indian independence movement Mahatma Gandhi stayed on visits to the city. The US President has cited Gandhi as a key influence.From there he meets captains of industry and entrepreneurs at a US-India Business Council forum, where he will stress the commercial opportunities offered by Asia, as he seeks to boost US exports to create jobs at home.

"The primary purpose (of the India trip) is to take a bunch of US companies and open up markets so that we can sell in Asia and some of the fastest-growing markets in the world," Obama told reporters on Thursday.

US exports to India have quadrupled in the last seven years to about 17 billion dollars a year, while service exports have tripled to 10 billion dollars a year.

Relations between the world's two largest democracies have warmed considerably in the past 10 years, but there are niggling disagreements over issues like US controls on the export of "dual-use" technology with military and civil applications.

Obama moves on to New Delhi on Sunday where he will meet Prime Minister Manmohan Singh and deliver an address to parliament on Monday.

The next morning he leaves for Indonesia on the second leg of his tour, which will also take him to the G20 summit in South Korea and then on to Japan.