LONDON (Reuters) - U.S. cable operator Comcast CMCSA.O has formally notified the European Commission of its intention to bid for Britain's pay-TV group Sky SKYB.L, starting the clock on a review, a regulatory source told Reuters on Monday.

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Comcast is racing to get ahead of Rupert Murdoch's Twenty-First Century Fox FOXA.O in the battle to buy the European company, and the notification in Brussels is a key requirement.

The Commission can clear the 22 billion-pound ($30 billion) bid with or without conditions or it can open a four-month investigation if it has serious concerns about the deal. The deadline for a decision is June 14.

Comcast, the world’s biggest entertainment company, stunned the industry in February when it made an informal bid for Sky, taking on Fox which is in the final stages of its own bid to buy the 61 percent of Sky it does not already own.

Comcast made its bid formal in April and the notification in Brussels starts the clock on the regulatory review. It is keen to show Sky’s investors that it can get through the regulatory process quickly, unlike Fox which has faced repeated delays since it first agreed a takeover of Sky in December 2016.

The Fox-Sky deal has been held up by concerns about the influence Murdoch could wield over public opinion through owning all of the broadcaster as well as British newspapers The Times and The Sun.

Fox has offered a raft of remedies to gain regulatory approval, such as protecting the independence and funding of Sky’s news division.

The original Fox-Sky combination has also been further complicated by Fox’s agreement to sell many of its TV and film assets to Walt Disney Co DIS.N, including its stake in Sky, for $52 billion (37 billion pounds).

Comcast has so far made the higher offer, at 12.50 pounds a share compared with Fox’s 10.75 pounds. Investors in Sky expect Fox to return with a higher offer if it can secure approval from Britain’s media secretary, who is reviewing that bid.

The regulatory source declined to be named because the process is not public. Comcast declined to comment.