The three-way global merger between SNR Denton, Salans and Fraser Milner Casgrain (FMC) will officially go live on 28 March this year, the firms have confirmed.

The three firms had originally targeted the first quarter of 2013 to complete their merger, following November's announcement of the combination.

Registration of the five profit pools under which the firm will be structured is expected to begin on 28 March, creating a firm with more than 2,500 lawyers across 52 countries.

The combined firm's Swiss verein structure will include distinct profit pools in the US; the UK, Middle East and Africa; Europe; Asia; and Canada.

As the firm – which will be known as Dentons – will not be fully financially integration, the major obstacle for its leaders will be to integrate the teams in Almaty, Brussels, London, Moscow and Paris where Salans and SNR Denton both have offices.

The deal is expected to see Salans' UK arm being absorbed into the City arm of SNR Denton, with the same happening in New York.

It is understood that practice head positions are yet to be decided.

The news comes as FMC's mining practice has lost a six-partner team, including securities head Michael Melanson and mining co-chair Sander Grieve, to the Toronto office of Bennett Jones.

Others in the 11-lawyer team include business law co-manager Linda Misetich Dann, corporate and securities partners Abbas Ali Khan, James Clare and Ali Naushahi, corporate senior counsel John Sabine and associates Elianeth Alicea, Jamie Au, Tiffany Canzano and Justin Park.

Merger discussions between SNR Denton, Salans and FMC started last year, with partners voting through the combination on 28 November, set to create a firm just outside the global top 10 by turnover, with combined revenues of around $1.3bn (£817m) and a large presence across the US, Canada, Europe and the UK.

The union effectively represents a four-way combination over three years, taking the 2010 union between US firm Sonnenschein Nath & Rosenthal and UK firm Denton Wilde Sapte into account.

A Legal Week survey carried out at the time of the announcement found scepticism of the tie-up from some in the market, with only 28% of respondents believing it to be a good deal, and 37% expressing doubts about the benefits touted by the three firms.