Miami Dolphins owner and Qatar to bid for Formula One -source

* U.S. sports tycoon and Qatar want 35.5 percent of Formula One

* Looking to acquire CVC (Taiwan OTC: 4744.TWO - news) 's controlling stake

* F1 chief says there are several potential bidders (Adds Breakingviews link)

By Freya Berry

LONDON, June 24 (Reuters) - The owner of the Miami Dolphins football team is joining forces with Qatar to buy a controlling stake in Formula One in a deal that could be worth up to $8 billion and inject new leadership into a sport facing falling TV audiences and ticket sales.

Dolphins owner Stephen Ross is looking to acquire a 35.5 percent stake from private equity fund CVC Capital Partners Ltd through his investment vehicle RSE, a source familiar with the matter told Reuters on Tuesday, adding that a deal could be done within six weeks.

Formula One impresario Bernie Ecclestone, who has ruled over the sport for four decades, would stay on to lead the racing side of the business, the source said.

The move comes as Formula One racing grapples with falling viewing figures, controversial race rules and soaring costs, all of which have led to some teams struggling for sponsorship.

The 84-year-old Ecclestone, a former second-hand car salesman and team owner, has been a controversial figure and last year agreed to pay a German court $100 million to settle a bribery case.

CVC has twice tried to float Formula One, most recently in 2013, but the plans stalled and the fund instead sold stakes to U.S. investment groups BlackRock (NYSE: BLK - news) and Waddell & Reed, along with Norway's Norges Bank.

It sold down its holding from 63 percent in 2012 in deals that at the time gave the business an enterprise value, which includes debt and equity, of $9.1 billion.

Ross has the backing of Qatar, which has been actively investing its wealth abroad, meaning that financing is unlikely to be a problem, the source said.

Ross' experience running sports in the United States could help Formula One build its presence there. Currently it only has one U.S. race in the calendar, in Austin, Texas.

Qatar is among those seeking a race but has so far failed to secure a slot with Ecclestone granting Gulf neighbour Bahrain an effective veto on regional rivals.

Qatar's success in securing the 2022 soccer World Cup has also become mired in controversy over the bidding process and corruption within the sport's governing body FIFA.

However, Qatar does already boast a sizeable presence in motorsport, including the MotoGP season opener among other championship rounds.

Dieter Hahn, chairman of the supervisory board of German sports marketing media group Constantin Medien (Xetra: 914720 - news) , is also involved with the investment consortium, the source said, adding that investment bank Leonardo is working with him.

Reuters could not immediately verify what Hahn's precise involvement was.

"The key to unlocking this deal is that under Bernie F1 doesn't do much TV rights marketing. Hahn will help with that," the source said.

"Bernie will do the teams, cars and racing. Dieter will do the media side."

LARGEST SHAREHOLDER

Constantin Medien brought a $100 million damages claim against Ecclestone in the London High Court over his involvement in the deal that brought CVC into the sport as top shareholder.

That claim was dismissed last year but the judge made damaging observations about Ecclestone in finding him neither a reliable nor truthful witness.

The lawsuit meant that due diligence on the deal now being negotiated needed to be done with particular care, because there were details that could not be shared with Hahn or Constantin Medien, the source told Reuters.

Goldman Sachs (NYSE: GS-PB - news) is working with CVC on the deal, while JP Morgan is working with the potential buyers.

Ecclestone told Britain's Times newspaper that three or four potential bidders had emerged.

"I have no idea whether any of these people have got closer with this, but CVC is in the business of buying and selling companies," he said.

No other parties were currently in talks with CVC, with RSE likely to walk away "if it turned into an auction" the source, who spoke on condition of anonymity, said.

Banks have not yet been brought in to finance the potential deal, the source added.

CVC and Leonardo were not available for immediate comment, while a spokesman for Hahn declined to comment. JP Morgan and Goldman Sachs had no immediate comment.

(Additional reporting by Sweta Singh and Alan Baldwin; editing by Ken Ferris and Louise Heavens)