It is expected that United will sign the players in the January transfer window.
“I’m going to Manchester to do a medical exam, but I will return in three days,” said Tosic.
“I hope everything will be okay, but I must confess that it’s hard to leave my club Partizan.
“When I was replaced in the game against Vojvodina, it was so strange and a hard feeling. I sat on the bench any said to myself this could be my last game for Partizan.
“But I hope that I will return one day. Of course, there is a big feeling of pride, I’m off to sign for the biggest club in the world, which is my favourite from my early years.
“My goal is to continue progress as footballer and I want to show Manchester United that my transfer wasn’t a bad thing.”
Ljajic added: “I was in Manchester once as a guest. I had a chance to look at how things are going on in a big club and now I will have another look.
“I’m staying in Partizan at least until the end of the season and then we will see what happens.”