Everton striker Romelu Lukaku turns down new contract amid Chelsea and Manchester United rumours

Everton striker Romelu Lukaku, the Premier League's leading scorer, is set to spark a transfer war in the summer after refusing to sign a record-breaking new contract at Goodison Park. The Belgium international had seemingly agreed a deal worth a reported £100,000-a-week – but has now made a dramatic U-turn amid interest from former club Chelsea and Manchester United.

The Guardian understands Lukaku has turned down the chance to become the best paid player in The Toffees' history and informed the club after training on Tuesday (14 March) ahead of the visit of Hull City this weekend. The 23-year-old has two years remaining on his current deal, but an exit this summer would allow the Merseyside club to cash in on his potential as one of the best young strikers in world football.

The Daily Telegraph understands that among the main issues in the negotiations between Everton, Lukaku and his agent Mino Raiola was the club's desire not to include a buy-out clause under £90m (€103.1m) in the contract. Chelsea, who failed in an attempt to bring Lukaku back to Stamford Bridge in the summer, and United are understood to be monitoring the situation and will have been encouraged by this latest development.

Raiola had confirmed in February that his client would be signing a new contract with Everton, which was expected to be a five-year extension. Manager Ronald Koeman threw the deal into doubt last week when he claimed there were no "guarantees" Lukaku would commit his long-term future to the club.

Both Chelsea and United are expected to launch bids to sign strikers in the summer transfer window, with Lukaku now likely to be a major part of their plans. Blues top scorer Diego Costa is braced to move to China following a mid-season falling out with Antonio Conte while Michy Batshuayi has failed to impress since his summer move from Marseille.

Costa was subject to a bid from the Chinese Super League in the January window but was eventually deemed unavailable due to a change in the number of foreign players allowed in each team's squad. Atletico Madrid have also made no secret of their desire to re-sign the Spain international.

Furthermore, United captain Wayne Rooney could also be on his way to Asia having been heavily linked with a move to the emerging footballing superpower. Zlatan Ibrahimovic is out of contract in the summer and manager Jose Mourinho has continually criticised his side's lack of a cutting edge, which threatens to undermine their bid to qualify for the Champions League.