Herbert Smith is set to strengthen its relationship with Cuatrecasas after it emerged its Iberian ally will be seconding a lawyer to Herbert Smith's Shanghai arm with a view to opening a closely-linked China operation.

Cuatrecasas senior associate Omar Alvarez will be seconded to Herbert Smith's Shanghai office while the Spanish firm waits to receive its formal licence to practise law.

The secondment is expected to take place before June next year and will mark the entrance of Cuatrecasas and its Portuguese arm, Goncalves Pereira Castelo Branco, into the Asian market.

It is understood the Spanish leader is considering taking up permanent residency in Herbert Smith's offices.

Cuatrecasas has been planning to open an office in the Asian market for some time as the Spanish giant moves to broaden its international scope in response to growing competition from international firms in its domestic market.

The Spanish firm has an informal referral relationship with Herbert Smith and has long been considered a prime candidate to join Herbert Smith's formal European alliance alongside German firm Gleiss Lutz and Benelux giant Stibbe.

Deals that have seen the two firms work closely together include Cuatrecasas' work for infrastructure and services group Ferrovial on its £440m acquisition of private equity firm Candover's stake in one of the world's largest aviation companies Swissport International in September 2005. Cuatrecasas brought in Herbert Smith to advise Ferrovial on UK aspects of the deal.

In late 2004, Herbert Smith called in Cuatrecasas to advise on Spanish law when it acted for US private equity firm Lindsay Goldberg & Bessemer on its 800m (£540m) acquisition of steel distributor Klockner & Co from WestLB.

One Cuatrecasas partner told Legal Week: "We will be opening in Shanghai with Herbert Smith. One of the representatives will be working from the Herbert Smith office and we expect a special relationship."