Shakhtar Donetsk midfielder Fred will compete a deal worth up to £52million next week.
United chief Jose Mourinho has won his battle to sign the 25-year-old star, who is considered to be suitable replacement for the retiring Michael Carrick.
Fred is with the Brazil squad which is preparing to win a sixth World Cup this summer.
He is letting his representatives thrash out his future while he dedicates his time to the Russia tournament.
Fred said: "I am focused solely on the World Cup. My agents are taking care of this."
He added: "It's an honour to be on the radar of great European coaches.