Manchester United striker Alejandro Garnacho is looking forward to his long-awaited debut with Argentina, saying his decision to represent the South American country is final.

Born in Spain but with an Argentine mother, the 18-year-old was called up for Argentina's friendly against Australia and did not hesitate at the prospect of playing alongside Lionel Messi with the World Cup champions in Qatar.

"I feel Argentinian, I am Argentinian. They bet on me and it was clear to me. It's a very big national team, a very good opportunity and my whole family is very happy and supported me from minute one," Garchacho told TyC Sports on Monday.

Garchacho, who had a brilliant season with United, suffered an ankle injury and missed the chance to be called up by Argentina coach Lionel Scaloni for friendlies against Panama and Curacao in March.

Last month he also missed out the chance to represent Argentina at the Under-20 World Cup held in the South American country after it replaced Indonesia as hosts.

"I talked a lot to the (Manchester United) coach (Erik ten Hag) and asked him to please let me go, but he said it was impossible. Still, I followed it on TV as if I was there," he added.

FIFA rules allow players with dual citizenship to change national teams as long as they have not played more than three matches (including friendlies), but with the possibility of still being called up by Spain, Garnacho said he is eager to pursue a career with Argentina.

"I don't need to play three games. I'm here and if I don't make my debut on the tour, it doesn't matter. I know I want to be with Argentina and it's going to happen,

"I want to make a career with the Argentine national team, if the coach trusts me I can keep coming. I want to be one more and take part in the Copa America, the qualifiers and the World Cup.

"I know that a lot of people in Argentina love me, appreciate me. I've already made the decision to play for Argentina, and I'm going to return that love on the pitch," he added.