Business secretary Vince Cable is at the site of an £82m development that will create hundreds of North East jobs.
The new factory, at Hitachi Rail Europe's plant in Newton Aycliffe, will be built by Darlington-based contractor Shepherd.
The firm will create 150 new jobs to construct the plant and secure hundreds more across the region's supply chain.
Vince Cable and Transport Secretary Patrick McLoughlin will open the development.
The region has received a £1.2 billion boost with the announcement of a new government contract to build trains.
270 carriages are to be manufactured by Hitachi Rail Europe at its new site in Newton Aycliffe.
Protestors gathered at Newcastle's Central Station to campaign against the proposed privatisation of the East Coast main line. Members of the National Rail Union have been at train stations across the country, including Newcastle and Berwick.
The Transport Secretary has announced that £1.2 billion will be invested into the manufacturing of carriages by Hitachi. The RMT says it is more about the bigger picture and that line has improved considerably under public ownership.
An order of 270 carriages has been placed with Hitachi. The class 800 series will be operated on the East Coast Main Line from 2019. The new Hitachi factory, in County Durham, is expected to begin manufacturing high speed trains from 2016.
The Transport Secretary, Paterick McLoughlin, has confirmed a £1.2 billion order for more state-of-the-art trains which, will be built at the Hitachi site in Newton Aycliffe.