The Government is "not backing away" from the High Speed 2 rail link between London and the north, the Transport Secretary will insist.
Chris Grayling will say the case for the controversial project is "as strong as ever" as the rail network rapidly approaches "crunch-point".
Creaking Victorian lines will be unable to cope with growing demand as the country's population continues to grow, he will tell a HS2 conference.
Mr Grayling will say: "We're not backing away from HS2. The case is as strong as ever.
"We need this railway. And if we're going to build it, let's make it state-of-the-art, fit for the decades of growth ahead.
"So that in 2033, we no longer have a rail network with a Victorian heart but a network with an Elizabethan heart, able to deliver everything we expect of a 21st century transport system."
MPs warned last month that ministers must set out a realistic timetable for delivering HS2.
The Public Accounts Committee (PAC) was ''not convinced'' that the target for completing phase one between London and the West Midlands by December 2026 will be met.
Its report also warned that cost estimates for phase two, which takes it from Birmingham to Manchester and Leeds, are ''still volatile'' and exceed available funding by £7 billion.
Mr Grayling will announce £70m of funding for road safety and support for communities affected by the line to the Midlands.
He will say: "We need HS2 now more than ever.
"We need it for the capacity it will bring on the routes between London, the West Midlands, Crewe, Leeds and Manchester, as well as the space it'll create elsewhere on our transport network.
"We need it for the boost it will give to our regional and national economies.
"And we need it for the jobs it will create, and for the way it will link our country together."
He will add: "We're facing a rapidly approaching crunch-point.
"In the last 20 years alone, the number of people travelling on our railways has more than doubled.
"And demand is set to increase still further. And it's not just about crowding in the carriages - it's also about crowding on the tracks themselves. Our rail network is the most intensively used of any in Europe."