Relive all Atlanta United's spectacular goals during their inaugural season in MLS. (2:05)

Independiente has reached an agreement in principle to send 18-year-old Ezequiel Barco to Major League Soccer side Atlanta United, sources have told ESPN Argentina's Alejandro Ruzal.

An MLS source told ESPN FC's Jeff Carlisle that a deal was "close" to being finalized, and the Argentine club confirmed Barco's exit in a farewell tweet.

Llegaste como un chico. Te formaste en la pensión y te vas como un hombre campeón.



Todo pasa, la gloria es eterna.



¡Gracias y éxitos, Ezequiel!#TodoRojo 🔴 pic.twitter.com/37EhUPVfUr — C. A. Independiente (@Independiente) January 12, 2018

"You arrived as a kid. You grew in the youth team and you leave as a champion," Independiente wrote. "Everything ends, glory is eternal. Thank you and success, Ezequiel!"

Independiente agreed to sell the budding star for an MLS-record $15 million plus 30 percent of any future transfer before December 2019, or 10 percent if Atlanta sells Barco after that date, according to sources.

The fee would smash the $10 million that Toronto FC paid Roma for Michael Bradley in 2013. Only a year ago, Atlanta also spent about $8.5 million to acquire Paraguayan standout Miguel Almiron from another Argentina club, Lanus.

The fee would also be the second-largest transfer fee for Independiente after the deal that sent Sergio Aguero to Atletico Madrid in 2006.

Ole reported that Barco would travel to the U.S. on Saturday to sign a five-year MLS contract.

Barco, who was under contract with Independiente until June 2019, helped his club win the Copa Sudamericana -- South America's second largest international tournament -- by scoring a penalty in the second leg of the final against Flamengo in December.

In the domestic Argentina league, the attacking midfielder scored five goals in 38 appearances over the past two seasons.

Ezequiel Barco is headed to MLS after winning the Copa Sudamericana, sources say. Antonio Lacerda/EPA

Reports of the deal have been swirling for weeks, with an Independiente vice president saying Barco wouldn't be sold for less than $20 million and Atlanta staying firm on a $12 million offer, but a compromise has now been reached.

The move continues a busy winter for Atlanta, which made the playoffs in its inaugural season under Argentine coach Gerardo Martino, while also breaking the MLS record for average attendance in a season at 48,200 fans.

The club has signed a pair of U.S. internationals in Darlington Nagbe and Greg Garza, and added to its formidable stack of young South American talent with defenders Franco Escobar, 22 from Argentina, and 20-year-old Jose Hernandez from Venezuela.

Almiron, 23, was named MLS's top newcomer of 2017 and also had the league's top-selling jersey. He is one of three designated players on the club along with Venezuelan star Josef Martinez, 24, and Argentine Hector Villalba, 23.