The express train will run between New Delhi and Silchar via Guwahati, New Coochbehar and Jalpaiguri in West Bengal.
The Railway ministry is starting a new weekly train service between Silchar and New Delhi from Saturday, a politically significant measure ahead of assembly elections in Assam later this year.
"The weekly Poorvottar Sampark Kranti express would be flagged off by Railway Minister Suresh Prabhu at a function in Silchar on Saturday," Northeast Frontier Railway (NFR) spokesman Pranav Jyoti Sharma told IANS.
The express train will run between New Delhi and Silchar (southern Assam's main commercial city) via Guwahati, New Coochbehar and Jalpaiguri in West Bengal.
Earlier on February 1, the Silchar-Sealdah Kanchanjunga Express began operations, meeting a long-standing demand of the people to link southern Assam with the country's mainland.
Southern Assam's Barak Valley was brought on the broad gauge rail map early last year. And a regular passenger train service between Silchar and Guwahati started on November 21 last year.
The 210-km Lumding-Silchar gauge conversion project, which was declared a national project in 2004, had been initiated in 1996.
The Lumding-Silchar line is the lifeline for southern Assam, known as Barak Valley, and the mountainous states of Tripura, Manipur and Mizoram. These states are heavily dependent on this railway line for supply of foodgrain, fertilisers, petroleum products, construction materials and other commodities.
Prabhu on Saturday will also flag off a freight train service from southern Assam's Badarpur station to Jirania (215 km) in western Tripura and Jiribam (75 km from Badarpur) in western Manipur.
This railway connectivity is the lifeline for millions in Tripura, western Manipur and Mizoram besides southern Assam, comprising four important districts.
The BJP-led central government is starting new trains to get electoral benefit, said Congress.
"The government wants to woo the electorate before the politically important assembly elections in Assam," Congress leader Tapas Dey told reporters.
The new service also comes ahead of the presentation on February 25 in parliament of the railway budget for 2016-17.