British billionaire Sir Jim Ratcliffe has agreed to buy a 25% stake in Manchester United for about $1.3bn (£1.03bn).

Ratcliffe's Ineos Group will take control of football operations.

The 71-year-old will also provide $300m (£236m) for future investment into the club's Old Trafford stadium.

The announcement comes 13 months after the club's owners, the Glazer family, stated they were considering selling to "explore strategic alternatives".

The American family bought the club for £790m in 2005.

The only other publicly declared bidder, Qatari banker Sheikh Jassim bin Hamad Al Thani, withdrew his offer to buy 100% of the club in October.

United have struggled on the pitch this season and have not won the Premier League since 2013, while there have been regular protests against the Glazer ownership.

Manchester-born Ratcliffe is chairman of petrochemicals company Ineos and says he is a "lifelong supporter of the club". He tried and failed to buy Chelsea last year..

In a statement, he said: "Whilst the commercial success of the club has ensured there have always been available funds to win trophies at the highest level, this potential has not been fully unlocked in recent times.

"We will bring the global knowledge, expertise and talent from the wider Ineos Sport group to help drive further improvement at the club, while also providing funds intended to enable future investment into Old Trafford.

"We are here for the long term and recognise that a lot of challenges and hard work lie ahead, which we will approach with rigour, professionalism and passion. We are committed to working with everyone at the club - the board, staff, players and fans - to help drive the club forward.

"Our shared ambition is clear: we all want to see Manchester United back where we belong, at the very top of English, European and world football."

The club say the deal is "subject to customary regulatory approvals" but are "hopeful it will be completed as soon as possible".

There is initially going to be a six-to-eight week process for the deal to be ratified, which includes being signed off by the Premier League.

How will the deal work?

Ratcliffe has agreed to buy 25% of the club's class B shares, largely held by the Glazer family, who own 69% of the club, and contain almost all the voting rights, and up to 25% of its class A shares, which are listed on the New York Stock Market. The shares are worth $33 per share.

It means the Glazer family will retain a majority stake in the club.

Taking on sporting control at the club means Ineos will oversee the men's and women's football operations and academies.

They will also get two seats on the Manchester United PLC and Manchester United Football Club boards.

Subject to necessary approvals, Ratcliffe will delegate his seats on the PLC board to John Reece, a shareholder of Ineos, and Rob Nevin, chairman of Ineos Sport.

On the UK club board he will delegate his seats to former British Cycling chief Sir Dave Brailsford and former Juventus and Paris St-Germain executive Jean-Claude Blanc.