The 19-year-old and reigning Football League player-of-the-year is expected to fly home from United’s pre-season tour of Ireland shortly with Leeds and Bournemouth close to an agreement for him.
Cook has been on Bournemouth’s radar for several months and Leeds resisted persistent interest from the Premier League club in January but United owner Massimo Cellino is ready to take a fee which will rise from around £6m.
The news will come as a serious blow to head coach Garry Monk who took Cook with him on tour to Ireland after asking the teenager to miss this summer’s European Under-19 Championship.
Cook was due to travel to the finals in Germany with England this month but Monk negotiated his withdrawal with Under-19s coach Aidy Boothroyd, saying Cook’s absence would be “detrimental” to his plans for his first season as Leeds boss.
Speaking to the club's official website on June 28, Monk said: "I spoke to Lewis and told him how important he is to this team and for the project going forward."
Confirmation of Cook’s likely departure arrived on the back of an encouraging day at Elland Road in which Leeds took their tally of summer recruits to six with the loan signing of Swansea City midfielder Matt Grimes and a deal for Oxford United forward Kemar Roofe.
Grimes, an England Under-21 international, has accepted a season-long deal while Roofe has signed on a four-year contract for a fee worth between £2m and £3m.
That sum is set to be dwarfed by the cash gained from the sale of Cook, a product of Leeds’ academy and a player who has been at the heart of United’s midfield for the past two seasons.
He made his debut in 2014, shortly after winning the European Under-17 Championship with England, and went onto play 85 times for Leeds. He took the Football League’s young player of the year award in April, a prestigious prize claimed previously by Gareth Bale and former United midfielder Fabian Delph.
Cook was tied to a two-year contract last summer, shortly after Cellino returned from a Football League ownership ban, but that deal expires in 2017 and United have not agreed an extension with him.
Leeds have come under pressure repeatedly over the years for failing to retain their better players and losing talented academy products, including Delph in 2009.
Right-back Sam Byram was sold to West Ham United in January following a breakdown in contract talks and Cellino cast doubt over the future of left-back Charlie Taylor tonight by attacking the 22-year-old for allegedly refusing to engage in negotiations about a new deal.
Taylor, like Cook, is out of contact in a year’s time and Cellino has previously stated that he had little confidence of agreeing improved terms.
Leeds would be entitled to compensation for Taylor next summer, unless the defender chooses to move abroad at the age of 23, and Cellino told the Mirror that he was not willing to allow him to move on in this transfer window.
Taylor’s agent, Colin Pomford, is the same agent who represents Byram and who was involved in a bitter fall-out with Cellino prior to Byram’s January exit.
Cellino said: “I'm very disappointed with the way he (Taylor) has acted. We are not going to let him go. Trust me.
“For almost one year, I've been trying to get him to sign a new contract. The agent is the same as Sam Byram's. But I promise, even if we lose him at the end of the season for free, I'm not selling him.”
Taylor is also in Ireland training with Monk’s squad. His agent has not responded to a request for comment.