Gonzalo 'Pity' Martinez has completed his move from River Plate to MLS Cup champions Atlanta United.

Martinez was a key player as River beat Boca Juniors to win the Copa Libertadores, scoring the clinching goal for his side in the second leg at the Santiago Bernabeu in Madrid.

The playmaker will now become the latest South American star at Atlanta, who appointed Frank de Boer as Gerardo Martino's replacement last month.

"I'm very excited to come to Major League Soccer and to join Atlanta United," Argentina international Martinez told the club's official website.

"The club has shown a lot of trust in me and I'm looking forward to working with Frank de Boer and my team-mates to continue making history at the club."

Martinez becomes Atlanta's fourth designated player, and with MLS sides only permitted to have three on their books it could pave the way for Miguel Almiron to move to Europe.

Paraguay international Almiron, compared to Gareth Bale by Atlanta chief Darren Eales, has been linked with Premier League side Newcastle United.

Vice president and technical director Carlos Bocanegra added: "We're excited to announce we've secured Gonzalo to a long-term contract with our club.

"Recently named as the best player in South America in 2018, Gonzalo is an attacking player who can play wide or centrally. His abilities complement our style of play and we expect him to make a smooth transition to MLS."