Chelsea have "serious and strong interest" in signing Manchester City striker Sergio Aguero, according to Sky sources.
The Blues will try to sign a striker this summer to replace Diego Costa, who has been told he is not in Antonio Conte's plans for next season.
After missing out on Romelu Lukaku, Chelsea have turned their attention to forwards such as Alvaro Morata (Real Madrid), Pierre-Emerick Aubameyang (Borussia Dortmund), Andrea Belotti (Torino) and Aguero.
Sky Sports News HQ understands it will be very difficult for Chelsea to sign Aguero with Manchester City reluctant to let him leave.
Since they were bought by the Abu Dhabi United Group in 2008, City have never sold a player against the club's wishes.
When asked if Aguero was staying in May, City chairman Khaldoon Al Mubarak said: "Absolutely. There's never been a doubt about that. I've read a lot of the speculation on this and it's ridiculous.
"Sergio Aguero is one of the best players in the world. We are a team that aspires to win every competition we compete in.
"Having Sergio Aguero as part of the squad is an absolute must. It has never been in doubt."
After Aguero, who was City's top scorer with 20 Premier League goals last season, netted twice in City's final game of the season - a 5-0 victory at Watford - manager Pep Guardiola also insisted he would not be sold.
"Every press conference [the question is asked]," said Guardiola. "Okay, guys. He will be [at City] next season. Happy? Good. Perfect."
Aguero was signed from Atletico Madrid for £38m in 2011 and has three years left on his current City deal.
He has scored 169 times for City in six years, winning two Premier League titles in 2012 and 2014.