The 21-year-old has spent the last two Premier League campaigns at West Bromwich Albion and Everton respectively, after finding it tough to break into Chelsea's first team since making an £18m switch from Anderlecht in 2011.
Amid reports that Blues boss Jose Mourinho does not plan to bring Lukaku back into the fold at Stamford Bridge, the Toffees and Tottenham Hotspur have been linked with an interest in recruiting the Belgian.
His Italian representative, Oscar Darmiani Jr, has indicated that this would have to be a permanent transfer, with Chelsea having ruled out another short-term solution, although he hinted that a new contract with the Londoners is also a possibility.
He told reporters: "Chelsea doesn't want to loan him out. He has two years left on his contract and we would normally look at extending it shortly."
Spurs and Everton would apparently have to pay around £20m for Lukaku's services this summer.