An HS2 construction firm boss has said he would be cautious about taking on future government projects amid doubts over the rail line's future.
Rising costs have led to speculation that the Birmingham to Manchester leg of the high speed line could be axed.
Mark Reynolds, of Mace Group, said it was "very rare" work on a major scheme "gets stopped", adding that working in the UK had been "challenging".
The government has said it is reviewing how costs of HS2 can be controlled.
The high speed rail project is intended to link London, the Midlands and the north of England. The first part, between west London and Birmingham, is already under construction.
But the scheme as a whole has already faced delays, soaring costs and cuts – including the planned eastern leg between Birmingham and Leeds which was axed in 2021.
Mr Reynolds, chief executive of Mace Group, said said he learned about the potential cancellation of HS2's Birmingham to Manchester link "like everyone else, about two and half weeks ago" in news reports.
There is also speculation over whether the line will end at Old Oak Common in west London, rather than carry on to Euston station in central London.
In March, Transport Secretary Mark Harper announced that work on a new station at Euston would be paused for two years as predicted costs had almost doubled to £4.8bn.
Mr Reynolds said the delay had been disappointing and came "from nowhere". Mace is part of a joint venture to overhaul Euston station for HS2.
"One minute the prime minister and the chancellor started telling everyone that the rail line is going to Euston and three weeks later, they said no, it's being paused for two years," he told the BBC's Today Programme.
"We had to demobilise over 1,200 people, designers, supply chain contractors on site."
On Wednesday, a group of Labour's regional mayors and the Mayor of London sent a letter to the government requesting a meeting before any decision is made on the future on HS2.
The leaders said scrapping or curtailing HS2 would "fail to produce any meaningful economic benefit", arguing that investment in transport infrastructure was "a huge driver of economic growth – creating jobs, increasing productivity and opening up new business opportunities".
"We agree on the importance of ensuring public money is well spent but it will be an international embarrassment and a national outrage if all this gets us is a line that leads to journeys slower than the current one between Birmingham and London and nothing more," the mayors said.
Mr Reynolds said it was "very rare that you work on a major scheme that gets stopped", adding it "doesn't normally happen in the UK, quite frankly at this scale".
The government is yet to make an official announcement on the fate of HS2, but there have been reports that Prime Minister Rishi Sunak has been alarmed by the rising cost of the project, with suggestions it could exceed £100bn.
The Times newspaper reported Mr Sunak was considering reallocating money to other regional transport projects, including the Northern Powerhouse Rail project which would include a mix of new and upgraded lines to speed up journeys between Liverpool, Manchester and Leeds.
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