Chelsea are monitoring Sergio Aguero's exit from Manchester City with the striker viewed as a possible alternative should they fail in their pursuit of Borussia Dortmund's Erling Haaland, sources have told ESPN.

City confirmed on Tuesday that their all-time record goalscorer will leave the club at the end of this season when the 32-year-old's contract expires.

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Sources have told ESPN that Aguero is considering interest from a host of top clubs across Europe with Barcelona thought to be leading the race to sign him.

It is unclear at this stage whether Aguero would entertain playing for another English club after spending 10 years at City, but sources told ESPN that Chelsea want to be kept informed of the situation should he indicate a desire to stay in the Premier League.

Chelsea's top priority this summer remains the pursuit of Haaland but that race will be fiercely competitive. The 20-year-old's father, Alf-Inge, and agent Mino Raiola were pictured in Spain this week heading for talks with representatives from Barcelona and Real Madrid.

Further meetings are expected in England and with other top clubs as Haaland assesses his options, although Dortmund are reluctant to sell this summer for less than €180 million.

ESPN reported on March 5 that senior figures at Stamford Bridge were bullish about their prospects of convincing Haaland to join but they have also drawn up a list of alternatives having recognised a need to further strengthen their forward line. Aguero and Inter Milan's Lautaro Martinez are among the names to have been discussed.

Olivier Giroud is expected to depart when his contract expires while talks have stalled with Tammy Abraham over a new deal.

Chelsea boss Thomas Tuchel wants to persevere with Timo Werner despite the Germany international's difficult first season in England -- the striker has scored twice in his last 31 games for club and country -- but there is a widespread agreement that reinforcements are required.

Tuchel was complimentary about Aguero when asked about Chelsea's interest with the two clubs set to face each other in an FA Cup semifinal later this month, a Premier League meeting at Etihad Stadium in May -- and a possible Champions League final after that with both clubs in the last eight.

"It is the same answer as for Haaland," he told a news conference on Friday. "We have full respect for Manchester City and for Sergio Aguero, who is a big player for them. There are no words needed from me about the achievements of this guy, he is a world-class player.

"But don't forget, we compete in three competitions for Manchester City so I will never speak about their players and talk about a player's future. It's their player and I expect they do the same with our players.

"We are rivals and, like I said, there are no words needed from me to praise Sergio Aguero's career. It is outstanding and speaks for itself. And it's not finished yet. He is still a player for City and will still help them to achieve their goals, which is a big collision to our goals because we are following the same things."