The Belgian international is out of contract at Old Trafford at the end of June and his future has been the subject of intense speculation.
"I am not worried about my contract running out, I am used to it. I am strong enough mentally to deal with it," Fellaini told reporters during Belgium's pre-match press conference ahead of their World Cup clash with England.
"Soon I will say where I will be playing next season. On July 1."
The former Everton midfielder has been linked with AC Milan, Arsenal and clubs in Turkey and China.