The 23-year-old has made only six appearances in the Premier League for Rafael Benitez's side this campaign.
"I persistently waited for the chance over the past months and I did not get it," Mitrovic said in the interview.
"I'm sorry – after all, I loved Newcastle, but it's time for me to look more to myself, to find the best solution for my career.
"I tried to be honest with myself and my teammates at every training and match. And the fact that I did not get a chance is simply not up to me.
"I never felt better. I'm physically in flawless form. I cannot wait to play. The most important thing is to find a club and finally get a chance in the field."
Mitrovic has made 72 appearances for Newcastle since his 2015 move from Anderlecht, scoring 17 goals and registering 10 assists for the Magpies.