Olswang and US tech leader Cooley have ended their alliance as the US practice weighs up options to launch its own presence in the City.

Management at both firms decided to call time on their 18-month non-exclusive alliance at the close of last year, although they are continuing to work on ongoing matters. It is understood the pair discussed a more formal tie-up or merger in the UK before calling off the relationship.

Instead, the top 60 US firm is now redrawing its London plans, with all options on the table – including an independent launch, a new alliance with a UK firm or a merger.

However, a merger could be difficult to achieve, given Cooley reported profits per partner of $1.3m (£820,000) in 2010 against turnover of $517m (£326m), putting profits significantly higher than most UK technology-focused counterparts.

Cooley has close relationships with a number of other UK law firms including Bird & Bird, Taylor Wessing and SJ Berwin, while Olswang is now expecting to broaden its US relationships. This could include the practice adding firms outside the technology sector – Cooley's primary practice focus.

Olswang chief executive David Stewart (pictured) said: "We have enjoyed working with Cooley over the past few years and we very much value the Cooley team, both as friends and colleagues with a shared technology focus.

"Of course, we also have good working relationships with a number of other US firms that focus on our core media and technology sectors."

The news represents the end of Olswang's second US alliance in recent years, after its relationship with Greenberg Traurig ended at the close of 2009 following Greenberg's launch in London earlier that year.