Romelu Lukaku is flying to London to complete his £97.5m (€115m) transfer to Chelsea from Inter Milan.
The 28-year-old underwent the first part of his medical in Milan after Chelsea agreed in principle a club-record deal to re-sign the striker.
The paperwork is now with club lawyers, and once that is formalised, Lukaku is expected to sign a five-year contract, worth £200,000 a week.
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Inter have previously rejected two offers from Chelsea for the Belgium international, the second of which was worth £85m (€100m) plus left-back Marcos Alonso.
Meanwhile, Roma have agreed a £34m deal to sign Tammy Abraham from Chelsea, according to Sky in Italy.
The 23-year-old striker must now decide if he wants to join the Italian club, who are managed by former Chelsea boss Jose Mourinho.
Fellow Serie A side Atalanta and Arsenal are also interested in Abraham, but Chelsea's preference is to sell him to a foreign club, making a move to their London rivals less likely.
Lukaku left Chelsea in 2014 after making just 15 appearances there following his arrival at Stamford Bridge from Anderlecht in 2011.
One of the most prolific strikers in Europe, Lukaku scored 87 goals in 166 games for Everton between 2014 and 2017 and found the net 42 times in 96 appearances during his two years at Manchester United before signing for Inter in 2019.
He scored 24 goals in Serie A last season, helping Inter to their first Scudetto in 11 years as the club put an end to Juventus' nine-year reign as Italian top-flight champions.
Chelsea will be keen to conclude the deal before 11pm on Tuesday so the player can be registered by UEFA to be considered for the Super Cup against Villarreal on Wednesday.
When the deal is completed, it will make Lukaku the most expensive player in history in terms of combined transfer fees, standing at a staggering £308.5m - over £30m more than Neymar in second (£271.7m).
Tuchel: Lukaku the profile we're looking for
Chelsea head coach Thomas Tuchel was reluctant to admit a deal for Lukaku was close, but did stress the No 9 role is an area the club are looking to strengthen after Olivier Giroud left the club to join AC Milan.
"We lost Olivier Giroud who played a crucial role in the club," Tuchel told Sky Sports. "He was the kind of profile who likes to play with his back to goal, who likes to hold up balls, who creates space for Werner, Havertz, Pulisic; who is ready to fight physically with defenders.
"This is the kind of profile that we don't have in our squad right now and that we are looking for. It's still not the moment to talk about names because we have nobody signed yet and we will show all the respect to other clubs.
"Romelu is one of the guys like Haaland at Dortmund, Lewandowski at Bayern, Harry Kane at Tottenham, who is a real No 9 who loves to score and who has a presence in the box. That is not a secret. The sentence [Tuchel describing Lukaku as a 'fantastic player'] is easy to repeat for any coach in the world.
"But [his] is the kind of profile we're looking for and if it is possible to convince agents and clubs, we will do our best."
Tuchel also stressed the need to improve after "big signings" elsewhere in the form of Jack Grealish to Manchester City and Jadon Sancho to Manchester United.
"They are big signings and we are also trying to improve the squad; at the same time we give all our energy to the guys that we have - it's our goal to improve the group we have," Tuchel added.
The evolution of Lukaku explained
His Belgium national team coach Roberto Martinez was among those to suggest there has been an evolution in Romelu Lukaku's game and one statistic highlights it best. Nobody in Italy provided more assists from open play than Lukaku did for Inter last season.
It is a statistic still viewed with scepticism by some and it is true that Lukaku's tally of 11 included a number of straightforward square passes and lay-offs. But other goals highlight the awareness, intelligence, vision and touch that carried Inter to the title.
It is a level of performance that has persuaded Chelsea to bring him back to Stamford Bridge one decade on from signing his first contract at the club. Lukaku, 28, returns at the peak of his powers, never better prepared to make a big impact on the Premier League.
'Lukaku deal almost done'
Sky Sports News' Kaveh Solhekol on The Transfer Show:
"We are very close, this is almost done. Lukaku is having his medical in Milan today, the first part of that is already over... As soon as the medical is done, he will be coming to London. It could be today, tomorrow, or the day after, but in reality, he is a Chelsea player.
"It is a fantastic move for him, 10 years after he signed for Chelsea. Last time around, it didn't work out. He was supposed to be the new Didier Drogba, he struggled and he was sold to Everton. But he's coming back a much better player, a more complete player.
"He is exactly what Chelsea need - a No 9. Thomas Tuchel said to the Chelsea board 'get me a No 9, I want Lukaku, Haaland, or Kane', and they've got Lukaku. They've had to pay a premium to get him and he is 28 - how much resale value is he going to have? I think he will still have some resale value if he was to leave Chelsea.
"But if he reproduces the form he has shown in Italy in the last two seasons, then Chelsea have got the answer to their problems because Lukaku will score 20 or 30 goals every season.
"This is the textbook example of how to make a transfer happen. You have to take your hats off to his advisors, his agents, because everything has been done properly. It has been done privately and behind the scenes, there has been no strikes and Lukaku has been very professional - he's always said the right things and it's going to be a good deal for Inter Milan."
Inter fans protest against owners - "Zhang, the time is over"
Inter must decrease their wage bill this summer and title-winning manager Antonio Conte left the club in May amid concerns about plans to reduce his budget.
Lukaku was not involved as Inter won 2-0 in a friendly away at Parma on Sunday evening - a match that witnessed prolonged protests against the club's Chinese owners over the planned sale and general cost-cutting strategy.
President Steven Zhang was the target of most of the anger with banners at the game saying "Zhang, the time is over" and "Zhang, if you want to save Inter you have to leave".
Chelsea are eager to sign a world-class centre-forward during the transfer window and Erling Haaland of Borussia Dortmund is another target the Blues have been interested in.
Meanwhile, with Lukaku set to depart the San Siro, Inter Milan are in talks to sign Roma forward Edin Dzeko and are offering the Bosnia and Herzegovina international a two-year deal.
Inter want to sign two forwards to replace Lukaku and one of their other targets is Atalanta's Colombia international Duvan Zapata.
If Atalanta sell Zapata, they will try to sign Tammy Abraham from Chelsea.
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