Jose Mourinho fears Manchester United are in for a "difficult season" if he is unable to add to his squad before Thursday's deadline.
United have only made one significant summer signing so far - midfielder Fred - with young defender Diogo Dalot and back-up goalkeeper Lee Grant also making moves to Old Trafford.
Mourinho has been linked with a multitude of players, most recently Leicester defender Harry Maguire, who United are preparing to make an offer for, according to Sky sources.
But, speaking before Sunday's friendly clash with Bayern Munich, Mourinho admitted to MUTV that he fears falling behind the rest of the top six if he is ultimately unable to add to his squad.
"My CEO knows what I want for quite a long time," Mourinho said.
"He knows what I want, I know that he tries to do the best for me and I still have a few days to wait what is going to happen.
"The other clubs who compete with us are really strong and have fantastic squads, like Chelsea, Tottenham or Manchester City, or they are investing massively like Liverpool, that are buying everything and everybody.
"And if we don't make our team better it will be a difficult season for us."