Cape Town - Romelu Lukaku says it is important for Manchester United to keep strengthening by making new signings next season.
The Belgian striker was one of the players signed by Jose Mourinho following his arrival at the club in a bid to reinvigorate the side following a few lean years.
Nemanja Matic, Victor Lindelof and more recently Alexis Sanchez have all arrived for big money this season.
However, Lukaku has backed his manager's recent claims that the squad is not strong enough to win major titles, following their exit from the Champions League this week.
United did manage to secure their place in the semi-finals of the FA Cup, but are well off the pace set by runaway Premier League leaders and close rivals Manchester City.
According to Lukaku, the club will again invest heavily in order to make manager Jose Mourinho happy.
"We are Manchester United, we have to improve every year and I know that a lot of players, a lot of good players, will come in next season. That's for sure," he said.
"That is something I look forward to, in order to improve the squad, and what the manager also looks forward to because next year we have to win.
"We will have to try and win as many trophies as we can."
Lukaku added though that he felt United were almost strong enough as a unit to be able to realistically claim some silverware, although he did feel Champions League opponents Seville were somehow a better side.
He added: "I don't believe we are really that short in being able to compete in the big competitions.
"We knew immediately after the game against Seville that we weren't good enough, so we accept the criticism."