Dentons is to merge with China's largest firm Dacheng, to create the biggest law firm in the world by lawyer headcount.

The deal, which is understood to have been approved by partners at both firms but is awaiting sign off from Chinese regulators, will be the second merger between a PRC firm and foreign player following the union of King & Wood and Australia's Mallesons Stephen Jaques in 2012, but the first of its kind for a firm with a significant US presence.

The combined firm will have a total of 6,500 lawyers across 50 countries, and will be known as Dentons outside China and Dacheng in China. The logo outside China will start with the Chinese symbols for Dacheng.

The global board of the merged firm will have 19 seats – representing all regions of the firm and will be chaired by Dacheng's director and founder Peng Xuefeng.

Dentons' global chair Joe Andrews will hold the same role in the combined firm, with Elliot Portnoy also retaining his title as global chief executive officer.

As with the King & Wood Mallesons tie-up, the firms will adopt a Swiss Verein structure in which they share resources, integrate along practice and client lines, but maintain separate profit pools.

All of Dacheng's lawyers outside China will join Dentons' offices, while Dentons lawyers in Hong Kong, Shanghai and Singapore will move to the Chinese firm's offices.

The combined firm will have a number of duplicate offices in addition to those listed above including: Chicago, New York, Los Angeles and Moscow.

Dentons, a transatlantic firm formed in 2013 via a merger between Canada's Fraser Milner Casgrain, Salans and SNR Denton, has long been in the market for a Chinese merger in a bid to fully tap Asia – where it currently has just 13 partners spread across four offices in Hong Kong, Shanghai, Beijing and Singapore.

Beijing head-quartered Dacheng, founded in 1992, is currently the largest law firm in China with more than 4,000 lawyers and 48 offices – seven of which are international and located in Chicago, Los Angeles and New York, Tapei, Singapore, Moscow and Paris.

In January last year, Joe Andrew, global co-chair of Dentons, unveiled to Legal Week the details of his bold expansion plans for Asia, which included mergers with firms in China, Japan, South East Asia and Australia.

In a later interview he said all international firms needed to be "bigger and better" in China particularly, and though he praised King & Wood Mallesons for having made the most progress, said the firm remained held back by its lack of relative US depth.

News of the Dentons China venture comes the same week that US rival Fried Frank decided to pull the plug on its Asian operations – highlighting the stark differences in law firm strategy when it comes to Asian investment.

In an internal memo to lawyers Fried Frank dubbed the region as currently "not sufficiently attractive from a commercial perspective", less than 10 years after a headline-grabbing market debut in which it hired eight partners from Simmons & Simmons.

Currently the Chinese legal market remains closed to foreign firms, allowing them only to have representative offices and advise on international law.

Some international outfits have managed to form alliances with local firms via Hong Kong and China's Closer Economic Partnership Arrangement (CEPA) or by committing to joint pitching arrangements, while others – such as Linklaters and Baker & McKenzie – are waiting on further details on the new rules for the Shanghai Free Trade Zone.

So far, the government has said that foreign firms and PRC outfits will be able to form "joint operations" in the zone and mututally dispatch lawyers to each others' offices, however, there has been no further clarity on what a joint operation means and whether this will allow financial integration.