BANGKOK: Manchester United striker Wayne Rooney will be out of action for a month after sustaining a hamstring injury on the club's tour of Asia and Australia.

Rooney suffered the problem during a training session on Thursday and when scans showed there was no chance he would be able to play during the tour, the England star was sent home to start his rehabilitation.

Wayne Rooney, left, arrives in Bangkok on Thursday. Credit:AP

"Following a scan this evening on a hamstring injury sustained in training, it has been decided Wayne Rooney should return home immediately for further assessment and rehabilitation," United said in a statement.

The 27-year-old now faces a race against time to recover for the start of United's Premier League title defence.