Britain is in talks with China over giving Beijing's state-owned railway builder a role in constructing the troubled HS2 high-speed link.
The China Railway Construction Corporation (CRCC) has said it can build the line in just five years at a much lower cost than is currently forecast, according to the Financial Times.
Department for Transport (DfT) officials confirmed early discussions had taken place between CCRC and HS2 Ltd, but said no "concrete commitments" had been made.
Last week the Prime Minister gave the project the go ahead, but the second phase of the line, from Birmingham to the north of England, would need to be reviewed.
It's currently set to cost more than £100 billion and be fully complete by 2040, although Boris Johnson has said he wants that brought forward to 2035.
The Financial Times reported that CCRC had written to HS2 Ltd's chief executive last month saying it could build the line by the middle of the decade, for a much reduced price tag.
The letter, first reported by Building Magazine and seen by the FT, states: "We are certain that we can offer a cost that is significantly lower than the projections we have seen.
"The advantages are too great, in our opinion, too great to dismiss on the basis that there are obstacles to overcome.
"You will find that the Chinese way is to seek solutions, not linger on obstacles and difficulties."
CCRC has transformed China's transport system, building most of the country's 15,500-mile high-speed network.
However, British officials are said to be sceptical that it could operate in the same way in a democracy with property rights, protected landscapes and powerful lobbying groups.
The project has already encountered fierce resistance by environmental groups who say the line will destroy large parts of the British countryside and threaten wildlife.
Any move to give Beijing a further role in the UK's infrastructure would almost certainly prove controversial, after Mr Johnson reportedly incurred the wrath of US President Donald Trump - as well as upsetting many Tory MPs - with his decision to allow tech giant Huawei to supply equipment for the 5G mobile network.