LONDON (REUTERS) - Manchester United manager Louis van Gaal has been warned as to his future conduct following comments he made about the referee after his team's 0-0 FA Cup draw at Cambridge United, the FA said on Wednesday.

The 63-year-old Dutchman said everything had been against Premier League United during the fourth-round match last month against fourth-tier Cambridge, including the referee.

Van Gaal denied the allegation that he was accusing the official of bias, saying had never been punished for criticising a referee in his long and successful managerial career.

United won the replay 3-0 and beat Preston North End 3-1 on Monday to reach the quarter-finals.