While management are insisting United must focus on a youth policy, Amorim is demanding proven players be found and signed for next season.
He said on Friday, "Manchester City and other teams are already in a place where we need a lot to catch them.
"I just want to focus on our strengths and use our club to bring one or two big players.
"We are doing all the stuff to be so much better next season, when we need to be so much better."
Amorim also conceded he is under pressure after a poor start to his United career.
"I hear a lot of people saying that Sir Alex Ferguson took three or four years to win something," he said. "But it's not possible these days because you have to give three interviews before every game. The pressure is so much different."