Manchester United will be Zlatan Ibrahimovic's biggest challenge, says coach Jose Mourinho

London: Manchester United`s marquee signing Zlatan Ibrahimovic will face the biggest challenge of his glittering career in the Premier League this season, manager Jose Mourinho has said.

Striker Ibrahimovic, who completed his move to Old Trafford last week, has won titles in four different countries, including at Inter Milan, where he played under Mourinho.

"Zlatan is Zlatan. He wins year after year," Mourinho told Manchester United`s website.

"His goal record is absolutely amazing, his passion for the game is incredible and it`s only possible with his passion and ambition, with his CV, to make the decision at this stage of his career, for the biggest challenge of his career."

Mourinho feels England`s top flight will pose new tests for the 34-year-old despite his spells at La Liga winners Barcelona and French champions Paris St Germain.

"It`s the biggest club he`s ever played for and the most difficult competition he`s ever played for. He is a massive player. I think it`s a beautiful thing when a coach has a player and, a few years later, has him again.

Ibrahimovic, Sweden`s all-time top scorer with 62 goals in 116 games, called time on his international career after his country was knocked out of Euro 2016 in the group stages.