SJ Berwin is set to pursue its long-mooted US merger with Proskauer Rose in a deal that would create a global top 30 law firm with combined revenues of over £600m.

As legalweek.com revealed on 6 May, Proskauer Rose had been identified as the sole potential US suitor after Orrick Herrington & Sutcliffe, another firm that SJ Berwin had considered a deal with, last week ruled itself out.

SJ Berwin’s discussions are being led by a small team including senior partner Jonathan Blake, managing partner Ralph Cohen and Paris managing partner George Pinkham.

A brief statement was issued to SJ Berwin’s partners late last week confirming the discussions, though the partnership so far has little detail. Any deal would have to be put to the City law firm’s partnership, with one partner saying it would require an overwhelmingly supportive vote to be passed.

Proskauer Rose recorded gross revenues of $643m (£428m) for its 2009 financial year while SJ Berwin posted revenues of £184m in 2008-09. The US firm’s average partner profits for 2009 were $1.36m (£900,000), down 12% on 2008.

Proskauer, which abandoned merger discussions with legacy UK firm Richards Butler in 2005, has since struggled to make an impact in Europe, with some former partners citing a lack of coherent strategy on the continent.

The firm, which outside of the US has a presence in Hong Kong, Sao Paulo, London and Paris, has built up its international presence on an office-by-office basis.

Proskauer launched in London in 2007 with the hire of O’Melveny & Myers private equity specialist Matthew Hudson. Hudson left the firm earlier this year leaving the City office with five partners, including highly-rated funds partner Bob Barry, who joined from Travers Smith in late 2009.