By Keith Weir

LONDON (Reuters) - U.S. asset management company Waddell & Reed increased its stake in the Formula One motor racing business to 20.9 percent from around 14.4 percent in a $500 million deal after the motor racing business put flotation plans on hold.

Private equity firm CVC, since 2006 the largest shareholder in Formula One, has now cut its stake to around 35 percent from 63 percent in deals in recent months.

The deals have helped to remove the pressure on CVC to try to list Formula One. The business put plans to float in Singapore on hold two weeks ago because of volatile markets.

"Several funds managed by Waddell & Reed Investment Management Company and Ivy Investment Management Company have today agreed to invest a further $500m in a private placement in Formula 1 at $9.1bn enterprise value," CVC said in a statement on its website.

CVC had previously cut its stake to 42 percent in a $1.6 billion deal announced in May with Waddell & Reed, BlackRock and Norway's Norges Bank Investment Management.

Formula One is a series of 20 high-speed motor races held around the globe that each draw a television audience in excess of 500 million.

Its revenues are expected to exceed $2 billion this season for the first time - helped by sponsorship and hosting fees which circuits pay for the right to stage races.

Formula One has the commercial rights to the sport for the next 98 years.

Briton Bernie Ecclestone, who retains a 5 percent stake in its business, is its commercial chief and is credited with turning the sport into a global money-spinner.

Ecclestone is 81 but has said he has no plans to step aside. Ahead of a planned flotation, Formula One appointed Peter Brabeck, chairman of food group Nestle, as its chairman.

Ecclestone told Reuters on May 31 that the plan was to list Formula One when "the time was right".

(Reporting by Keith Weir; Editing by John Stonestreet)