Mumbai, Nov 6 (IANS) The US Air Force One carrying President Barack Obama and his wife Michelle is expected to touch down at Mumbai airport shortly before 1 p.m. as they begin their four-day India visit Saturday amid a tight security blanket.

After he lands at the Chhatrapati Shivaji International Airport Obama will board an American chopper to go to the Indian Navy base helipad in south Mumbai.

Apart from Michelle, he will be accompanied by top officials in what would be the president's longest foreign trip since he assumed presidency two years ago.

Obama, who will spend the night in Mumbai, will stay at the sea-side Taj hotel, the most prominent landmark attacked by Pakistani gunmen in November 2008 in a ghastly show of terror that left 166 dead.

As per his schedule, still described as "tentative" by authorities, President Obama will reach Taj Hotel by 1.30 p.m., and will go to Mani Bhavan, where Mahatma Gandhi used to stay and which is now a museum, around 2 p.m.

He will then go to the Hotel Trident-Oberoi for an interaction with the captains of Indian and American businesses, around 4.30 p.m., followed by an address to the US India Business Council Summit, billed to be the most important business engagement.

Simultaneously, First Lady Michelle Obama would interact with the youth and students at the University of Mumbai at around 4.30 p.m.

Security was tight in Mumbai as several arterial roads, approaches to and from railway stations have been either completely sealed off to traffic, or blocked or made one-way in view of the presidential trip -- measures that could inconvenience lakhs of people.

The security restrictions shall be felt acutely when hundreds and thousands of people move out of their homes to celebrate 'Bhai Beej' Sunday.

Besides traffic movement and parking, stringent restrictions have been imposed on pedestrian movement and functioning of shops and establishments in the entire five kilometre radius that the Obamas would 'occupy'.

Even public transport, including buses and taxis shall be restricted in large parts of south Mumbai, dealing a blow to cabbies who generally expect a Diwali windfall.

All tourist boats to and from Elephanta Island and harbour ferries at Gateway of India have been stopped since Friday in view the president's halt at the Taj hotel.

On Sunday, President Obama will visit the Holy Name School, Colaba, interact with students, celebrate Diwali, and probably light a candle, and view a dance programme by students.

From there, he will go to the St. Xavier's College at around 10 a.m. and interact with select students from six city colleges.

Obama will also go around an exhibition on agriculture in the college premises and also meet some agriculturists.

The US first couple depart Sunday afternoon for New Delhi for two days of hectic engagements, including talks with Prime Minister Manmohan Singh. He leaves for Indonesia Tuesday.