Chelsea sign Chicago Fire, USMNT youth goalkeeper Gabriel Slonina

Chelsea have completed the signing of Chicago Fire and United States youth international goalkeeper Gabriel Slonina, it was announced Tuesday.

Sources confirmed to ESPN on Sunday that the clubs agreed the transfer for a base fee of $10 million that could rise to $15m with add-ons. Chicago will also retain a percentage of any future transfer fee Chelsea receive for Slonina.

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Slonina will continue with the Fire on loan for the remainder of the MLS campaign and head to Stamford Bridge on Jan. 1. He has signed a six-year contract with the London club.

"I joined this club with ambitions of playing at the highest level and it's been a dream come true to wear the Chicago Fire jersey," Slonina said in the Fire's release. "This club has become my second home, my second family, and there are so many people that have played a big role in helping me get to where I am today. I'm so thankful for all the support that I've received from my family, coaches, teammates, and everyone associated with the club. It's been an incredible honor to work alongside each one of you."

"To the fans, I want to thank you all for supporting a local boy from Addison. You have inspired me to work my hardest day in and day out. I promise that I will continue to give everything in these final 11 games to help get us back into the playoffs and compete for a championship."

Slonina has long been considered one of the brightest talents of the Fire's academy and took over the starting goalkeeper spot with the first team last season as a 17-year-old. When Slonina made his professional debut, he became the youngest starting goalkeeper in league history at 17 years, 81 days.

The U.S. youth international has made 34 appearances for the Fire, keeping 14 clean sheets.

Slonina has figured multiple times for the U.S. at youth level. In May, he declared his intention to continue to represent the nation despite having a Polish passport through his parents.

The American joins Chelsea as the club's third signing this summer, alongside Kalidou KoulibalyandRaheem Sterling.

Also on Tuesday, Chelsea announced that they had agreed a deal to sign England Under-19 midfielderCarney Chukwuemeka from Aston Villa. Sources told ESPN that the teams had agreed an initial 15 million fee, which could rise to20m.