United said that the transfer was subject to the agreement of personal terms, British visa requirements and a medical.

The 30-year-old is set to sign a four-to-five year deal at United with wages of around 16 million euros ($A23 million) per year.

British media said on Friday that United had closed on a deal worth up to 70 million euros ($A102 million) for Casemiro, who has 63 caps for Brazil.

Earlier, Real coach Carlo Ancelotti said Casemiro wanted to leave Real to face a "new challenge".

"We understand his feeling, I do not think there is a way back," Ancelotti had told a news conference earlier on Friday.

"Real Madrid loses a player that has linked really well with the other midfielders with more quality, (Luka) Modric and (Toni) Kroos. He is important and has been key to Madrid's success," Ancelotti said.

Casemiro's addition will boost United's options in midfield, with manager Erik ten Hag currently having only Fred and Scott McTominay as the regular players in that department.

United are bottom of the Premier League after losing both their opening games. They host rivals Liverpool on Monday night.

LaLiga and European champions Real signed France midfielder Aurelien Tchouameni in June from AS Monaco, with the 22-year-old believed to be a replacement for Casemiro.

After joining the Spanish giants in 2013 from Sao Paulo, Casemiro has won five Champions League trophies, three La Liga titles, one Copa del Rey, and three Club World Cups among other honours.

Australian Associated Press