Sao Paulo are keen to hold on to the 19-year-old midfielder despite being a major target for top European clubs. A £25m bid was also rejected from United, who have officials in Brazil trying to work out a deal, and Inter Milan's £20m bid was turned down.
Meanwhile, reports suggest that United are willing to increase the bid to £34 million. However, Sao Paulo president Juvenal Juvencio is not ready to sell the young star.
Sources close to the club said, "Football is about winning titles and there is nothing more important. He will be an important player in any titles this club may win."
"What matters in football is what you achieve on the pitch, not how much you have in the bank. We have decided that Moura will be an important part of the trophies we want to win."
Lucas, who arrived in London on Tuesday to participate in the Olympic games, earns less than €100,000 a month and is in the process of signing a contract extension with Sao Paulo.