Transport Secretary Grant Shapps has said "any outcome is possible" on HS2 amid fears the project could be scrapped after a review into its future is completed.
The next steps for the project and whether it is going to happen are something "we will know the answer to" by the end of the year once a Government-commissioned independent review has been looked at, he said.
On whether HS2 could be scrapped after the review, Mr Shapps told Sophy Ridge on Sunday said that "once you start with a blank piece of paper and you say to the person doing the review and his team, 'give me the facts', then any outcome is possible from that, yes".
The review, which has been launched amid growing concern that HS2 cannot be built to its current specification within the #55.7 billion budget, is being led by former HS2 Ltd chairman Douglas Oakervee with Lord Berkeley - a long-term critic of the high-speed railway scheme - acting as his deputy.
Mr Shapps said: "Just because a project has already taken a lot of money, and even if the projections continue to rise in terms of the costs, it cannot be right not to stop and take a look at it.
"We are spending taxpayers' money and that money can only be spent once, so you have got to spend it wisely."
Andy Burnham, the Mayor of Greater Manchester, told Sophy Ridge on Sunday: "If this review is about building the right railway for Britain in the 21st century at the right cost and minimising waste, that's OK, I will support that because I still have some concerns about the design and the cost of HS2.
"However, if this review is about scrapping it, then the Government had better get ready for an almighty fight with the big cities of the north and, I understand, the Midlands too."
Liverpool BID chief executive Bill Addy has said the latest announcement "spreads doubt, uncertainty and frustration among business leaders in the north".
The Department for Transport (DfT) has said the review will consider a number of factors relating to HS2, including its benefits, impacts, affordability, efficiency, deliverability, scope and phasing.
A final report is to be sent to Mr Shapps - with oversight from Prime Minister Boris Johnson and Chancellor Sajid Javid - by the autumn.