The United Kingdom is in talks with China to give the Beijing railway manufacturer a role in the construction of the HS2 high-speed rail line.
The Chinese state railway company said it could build the line in just five years and at a much lower cost, according to a letter from Building magazine.
Government officials said that "preliminary discussions" had taken place, but that no "concrete commitment" had been made.
It comes after Boris Johnson this week approved the controversial plan.
And despite an official review, warning costs could reach more than £ 100 billion, compared to a budget of £ 62 billion.
According to current plans, the last stretch of the line is not expected to be completed until 2040 - although Johnson said he wanted it to be postponed to 2035.
However, Building magazine reported that the China Railway Construction Corporation (CRCC) wrote to the CEO of HS2 Ltd last month, saying it could build the line by the middle of the decade, for a price. very reduced.
Any decision to give Beijing an additional role in the infrastructure of the United Kingdom would almost certainly be controversial, after Mr Johnson angered US President Donald Trump - as well as upset many Conservative MPs - with his decision to authorize tech giant Huawei to supply equipment. for the 5G mobile network.
The CRCC letter has also been seen by the Financial Times, saying, "We are certain that we can offer a significantly lower cost than the projections we have seen.
"The benefits are too large, in our view, too large to be discounted on the grounds that there are obstacles to be overcome.
"You will find that the Chinese way is to seek solutions, not to dwell on obstacles and difficulties. "
CRCC has transformed China's transportation system, building most of the country's high-speed network.
However, British officials would be skeptical that it could function the same way in a democracy with property rights, protected landscapes and powerful lobby groups.
Supporters of HS2 say it will improve transportation times, increase capacity, create jobs and rebalance the British economy.
Once built, the routes will be shorter. Travel time from London to Birmingham will be cut from one hour, 21 minutes to 52 minutes, according to the Department of Transport.
And during its construction, it is expected to create thousands of jobs and stimulate economic growth.
An official with the Department of Transport said, "The DfT is always eager to learn from the experience of others and to consider approaches that offer value for money to the taxpayer. "