The two games that have been postponed are the ones that were played on 11 December.
The training ground for Manchester United was closed because of a rise in coronaviruses.
The first-team section of United's facility was shut down last week.
The players have returned to training.
The English Football League and the Premier League decided to go ahead with their festive fixture on Monday.
The Manchester United statement said that the games were postponed because the club had no option but to request that the matches be rearranged.
The fixtures were called off due to guidance from medical advisors.
The reopening will give the squad time to prepare for their next game against the Tynesiders at St James' Park on Monday, December 27th.
A number of positive Covid tests were recorded by Manchester United after their 1-0 win at Norwich on 11 December.
The league confirmed this week that there had been 90 new positive cases of players and staff who had been tested between 13 and 19 December.
