Scrapping the high-speed rail link HS2 would be a "disaster" and prevent a transformation of the road and rail network, a strategy group has said.
The government is to examine the costs and benefits of the project and make a decision on its future later this year.
Although a review will "rightly scrutinise" the scheme, Midlands Connect said HS2 must not be dropped or the scope of the scheme changed.
But farmer Robert Lockhart who has lost land to HS2 said it was a "whitewash".
Phase 1 of HS2 between London and Birmingham is due to open at the end of 2026, with a second phase to Leeds and Manchester scheduled for completion by 2032-33.
The government approved the scheme in January 2012, but last month the project chairman reportedly warned its cost could rise by £30bn and said it cannot be delivered within its £56bn budget.
Midlands Connect, which works with local authorities and enterprise partnerships on the region's transport strategies, said the "massive benefits of HS2 to the Midlands" were already being felt.
Its director Maria Machancoses said: "We must not lose sight of the fact that HS2 will transform our transport network for the next century."
She said scrapping the project would "be a disaster for the Midlands and the whole country".
But farmer Mr Lockhart, who has lost about 35 of his 280 acre farm on the Staffordshire/Warwickshire border to the project said he felt the scheme would not go ahead in full.
"There are so many people and companies involved that no-one knows what they're doing and they're chucking money at it and I've noticed such a waste of resources and time," he said.
"They've made so many promises over it and now the government is so fragile."
Lottie Jones, a campaigner for Ruislip Against HS2, said she was glad the new Prime Minister Boris Johnson, who is her local MP, was "taking HS2 seriously".
But she said she doubted the independence of the "long overdue review".
"It is not too late to stop HS2. Even if billions have already been spent it would be better to put it out of its misery now than waste tens of billions more," she added.
Ted Pawley, 69, who is a Perivale resident and campaigner against HS2, said he thought the review was "fantastic news."
"All these people who are for HS2 are the investors, living miles away from where all this will be happening, trying to convince us that we want this when we don't, not yet anyway.
"Let's spend that money on things we really need like improving the NHS, on schools."
The rail network is due to arrive in Crewe by 2027 and the station will become a hub when the line later extends to Manchester.
Earlier this month, it was revealed a £137m extension to the West Midlands Metro passing underneath Curzon Street Station - a yet-to-be-built hub for the proposed route - had been delayed by HS2.
Curzon Street is due to open with seven high-speed platforms in 2026 and the Department for Transport said work would continue at the site during the review.
By Phil Mackie, BBC News Correspondent
Work is already under way at Curzon Street in Birmingham to prepare the ground for where the new HS2 terminal will be built.
Besides the facade of the old Victorian station and the sound of diggers there isn't much to see. However if you look back towards the city it becomes clear what HS2 means to Britain's second city.
The skyline is filled with new office buildings and hotels which in turn are surrounded by more than a dozen giant cranes which are building the next developments.
Many of those businesses which have already relocated to Birmingham, or are planning to do so, have made the decision based on the promise of faster connections to London and beyond.
If the project were scrapped or downgraded it's feared that the city's great revival will falter or stop.
However, if you live along the route and have seen little or no benefit from the new high speed rail line then today's announcement may be more welcome.
The government's review will be chaired by Douglas Oakervee, a civil engineer and former chair of HS2 Ltd.
West Midlands Mayor Andy Street, who will be part of the panel, said he was behind the review and was confident the scheme would go ahead.
He said: "HS2 is mission critical for the West Midlands as it will free up the capacity we so desperately need on our existing railways, drive huge economic growth, and is already creating jobs and building new homes in the region."
Leader of Birmingham City Council, Ian Ward, said "a U-turn would be disastrous" and he would be making the case for the city when he meets Mr Oakervee.
"HS2 is about so much more than fast trains to and from London," he said.
"It's about jobs, homes and life chances. It's a once in a lifetime opportunity to rebalance the UK economy."
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