UPDATE 1-DAZN in advanced talks to buy BT Sport, FT says

(Adds DAZN declines to comment, background)

LONDON, Sept 21 (Reuters) - DAZN, the sports streaming service owned by billionaire Len Blavatnik, is in advanced talks to buy the sports television unit of Britain's BT to gain content including English Premier League soccer, the Financial Times said on Tuesday.

DAZN Chairman Kevin Mayer said last week he was "possibly" interested in BT Sport, telling a TV industry conference that he would "love to have EPL (Premier League) ultimately" and BT Sport was a "great business".

A BT spokesperson said the company was continuing to explore options for BT Sport, and all possibilities remained on the table, including a total or partial sale or retaining the business.

A spokesperson for DAZN declined to comment.

A source close to the negotiations said a deal was "not at the line yet", given the complexity of the rights and agreements involved, such as a reciprocal partnership with BT's rival Sky.

BT said in April it had put the unit on the block, and had appointed Lazard to explore options.

DAZN was high on analysts' lists of likely bidders, alongside broadcasters including Disney and ITV.

In a blow to Sky Italia, DAZN in March secured the right to screen all Serie A soccer matches in Italy for the next three seasons for 2.5 billion euros ($3 billion).

The company is under fire, however, about its service. Some users have complained about interruptions to streams, and the national communications authority is monitoring DAZN's pledge to boost its infrastructure.

BT spent billions of pounds on Premier League and Champions League rights for BT Sport to take on Britain's dominant sports broadcaster Sky.

The company said in May that BT Sport had a clear market position and was performing well. But with its focus turning to building its fibre network, it was exploring options to continue growing the unit. (Reporting by Paul Sandle and Elvira Pollina Editing by Mark Potter)