Manchester United forward Zlatan Ibrahimovic has come to the United States to undergo surgery on his knee injury in a bid to save his career.

Ibrahimovic damaged knee ligaments during the 2-1 Europa League quarterfinal victory over Anderlecht last week. There has been speculation it could end the 35-year-old's career, although the striker vowed on Instagram this week to "come back stronger."

United manager Jose Mourinho would not say speculate on Ibrahimovic's future but confirmed to Sky Sports that the striker was in the U.S.

"He is in America and that's the only thing that matters now," Mourinho said. "He is in America to have the surgery and start the recovery process."

Sources confirmed to ESPN FC that Ibrahimovic made the trip to Pittsburgh to see knee specialist Freddie Fu.

Zlatan Ibrahimovic was injured as Manchester United beat Anderlecht in the Europa League. OLI SCARFF/AFP/Getty Images

Ibrahimovic, who has scored 28 goals in 46 games this season, will miss the rest of the campaign.

He is out of contract at the end of the season, although Manchester United do have the option of extending his deal for a further 12 months. Mourinho had been keen to extend the former Paris Saint-Germain forward's stay at Old Trafford, but it is still unclear whether the injury will affect the offer on the table.

Ibrahimovic has been linked with a move to MLS side LA Galaxy and has been coy about his future before injuring his knee. And Chicago Fire midfielder Bastian Schweinsteiger has called on Ibrahimovic to follow him in making the move from United to Major League Soccer.

On Monday, Ibrahimovic received well-wishes from his former AC Milan teammate Ronaldinho.

"My friend Zlatan Ibrahimovic, I wish you all the strength in this difficult time," Ronaldinho wrote on Instagram. "I'm hoping for your speedy recovery and hope to see you soon, charming us with your football."