City firm Denton Wilde Sapte and US firm Sonnenschein Nath & Rosenthal are set to merge to create a 1,400-lawyer transatlantic firm.

The merged firm would have combined revenues of around £500m and would span 18 countries.

The firms’ management boards have recommended the merger to partners, who will vote on whether to give the green light on 9 June. Any merger would become effective on 30 September.

Dentons chief executive Howard Morris and Sonnenschein chairman Elliott Portnoy would become co-chief executives of the new firm, SNR Denton. Dentons chairman Martin Kitchen and Sonnenschein business and regulation chair Joseph Andrew would become co-chairmen of SNR Denton.

SNR Denton would focus on eight practice areas: financial institutions and funds; energy, transport and infrastructure; insurance; real estate, retail and hotels; technology, media and telecommunications; health and life sciences; manufacturing; and government.

Morris said: ‘Neither of us was interested in pursuing a combination just for the sake of increasing headcount and offices – this is not about dots on a map. The end goal for both firms was enhancing legal quality and client service, while also creating a strong global platform. Our newly branded firm will achieve all three objectives.

‘Our two firms already share a number of complementary features – our respective practice strengths, our focus on highest-quality client service, and especially our cultures.’

Portnoy said: ‘This combination is the next step in our vision to create an elite, client-focused international firm that is about one thing – quality. Both firms have long enjoyed reputations as being world class, and now together we’ll have the assets and professional resources to carry that forward to new sectors, new practices and new markets. As one firm, we will be able to serve our clients better.’

Sonnenschein acquired more than 100 lawyers from former New York firm Thacher Proffitt & Wood in 2009.