Global outfit Dentons has announced a merger with US firm McKenna Long & Aldridge, 18 months after previous talks on a potential tie-up failed.

The alliance builds on Dentons’ landmark deal in January with China’s largest law firm Dacheng, which created the biggest legal practice in the world by headcount.

McKenna Long is a 15-office Atlanta-headquartered firm with 430 professionals, known for government contracts and public policy work. The combination will create a law firm of around 6,600 lawyers and professionals, including 1,100 in the US.

Dentons’ global turnover in 2013 was $1.3bn (£0.86bn). The firm has about 450 fee-earners in the UK, based in City of London and Milton Keynes offices.

Dentons US will be led by co-chief executive officers Jeff Haidet, chairman of McKenna Long, and Peter Wolfson, CEO of Dentons US. Mike McNamara, managing partner of Dentons US, will be the managing partner of the merged Dentons US.

The merger will take effect later this year.

Wolfson said: ‘Last year Dentons enjoyed the best financial performance of our 109-year history in the US. Combining with the exceptional lawyers and professionals of McKenna Long continues our strategic priority of bolstering that performance in practices such as corporate, litigation, intellectual property, public policy and regulation, and many other critical areas of client service.’

Dentons has yet to unveil 2014 financial results.