A Californian private equity firm has edged closer to becoming the new majority-owner of Chelsea Football Club after securing a period of exclusivity to clinch a deal.

A group spearheaded by Todd Boehly, the LA Dodgers part-owner, overcame opposition from rival consortia on Friday to land preferred bidder status in the battle to replace Roman Abramovich as the Blues’ owner.

Mr Boehly’s bid would see voting rights shared equally between him and Clearlake Capital, a Californian private equity firm.

Clearlake, which has no direct ownership pedigree in major sports assets, would own a majority of the shares in Chelsea, Sky News revealed last week.

The group is being advised by Goldman Sachs and Robey Warshaw, where the former chancellor – and Chelsea fan – George Osborne, now works as a partner.

Sources said that Mr Boehly’s group’s exclusivity period, which was first reported by the Wall Street Journal, would last several days.

On another day of behind-the-scenes drama at Stamford Bridge, however, the British petrochemicals tycoon Sir Jim Ratcliffe said he had offered £4.25bn to buy Chelsea – despite having said publicly as recently as this year that the club was overpriced.

Sir Jim’s entry into the race to buy Chelsea is thought to have come too late, although there remains a possibility that he could buy Chelsea if the Boehly-led bid is unable to be completed.

Mr Boehly’s group is understood to have agreed to a request from Mr Abramovich – reported by Sky News on Thursday – that its bid be increased by £500m to boost the cash being donated to a foundation being set up to benefit victims of the war in Ukraine.

A spokesman for Mr Boehly’s bid declined to comment.

It was unclear on Friday whether the financing structure of Mr Boehly’s offer with Clearlake had altered as a result of the request for the additional £500m.

Already this week, manager Thomas Tuchel has said that the sanctions against the club’s owner were to blame for Antonio Rudiger, the German central defender, for deciding to leave in the summer.

Earlier this week, the three remaining bidders reaffirmed a commitment that they would not sell a controlling stake in Chelsea for at least a decade.

That request, which is thought to be unprecedented in a football club auction, was allied with one for minimum further investment of £1bn in its stadium, academy and women’s team.

The demands highlight the unusual nature of the Chelsea sale process at a time when the ownership of English football clubs faces unprecedented scrutiny and government intervention.

On Monday, ministers published their response to former sports minister Tracey Crouch’s report on football governance, paving the way for the establishment of a new independent regulator for the sport.

Mr Abramovich has owned Chelsea since 2003, and has turned the club into one of the top sides in Europe, with 19 major trophies having been won under him.

The two defeated consortia were headed by Boston Celtics part-owner Steve Pagliuca and Larry Tanenbaum, the NBA chairman and Toronto Maple Leafs owner; and Sir Martin Broughton, the former British Airways and Liverpool FC chairman, which would have involved Harris Blitzer Sports & Entertainment – owner of a stake in Premier League side Crystal Palace and a string of US sports teams – holding a controlling interest.

The last eight weeks have witnessed a bidding frenzy unprecedented in English football, with billionaire financiers, media tycoons, and sports team owners from several continents joining forces in an attempt to gain control of the Blues.

Raine Group, which is handling the sale process, declined to comment.