The two consulting engineers have worked together in recent years on major UK infrastructure works, including the London Olympic Games, as delivery partner on HS2 phase one and early design for Crossrail 2.

According to a report in the Times today CH2M is believed to have made a senior level approach at the end of last year to explore whether a tie-up could work. But it is unclear how far talks developed.

CH2M expanded in the UK back in 2011 when it scooped up another engineering consultant Halcrow.

The US firm is the largest of the two businesses employing about 25,000 employees in more than 50 countries, with around £4.3bn revenue. Atkins has more than 18,000 employees helping to generate about £1.9bn in turnover.

Both engineering groups have a global reach with Atkins keen to expand in Denver-based CH2M’s home US market.

Likewise CH2M could benefit from Atkins’ UK presence as well as gaining access to European markets such as Scandinavia, where Atkins is one of the top engineering and design consultancies.

Both groups would also strengthen their presence in the Middle East and Asia-Pacific.

“It is our policy not to comment on rumour and speculation,” said an Atkins spokesman.