The 18-year-old has emerged as a hugely promising midfielder under Erik ten Hag at Old Trafford and started his 10th consecutive match across all competitions on Sunday as United beat Aston Villa 2-1 at Villa Park.
Mainoo has represented England at under-17s, U18s and U19s level but is eligible to switch his allegiance to Ghana, where his parents were born.
The youngster still spends some of his spare time back in Ghana and the country’s football association confirmed earlier this month they were keen on convincing Mainoo to represent them at international level.
However, sources have told ESPN that Southgate believes Mainoo has significant potential and is keen to accelerate his progress with England.
Southgate will name his senior squad on March 14 and there is a chance Mainoo could be included should he continue his superb form for United, although it is equally likely at this stage that he could skip the U20s and move into England’s U21s squad.
Mainoo’s involvement will be one key topic of conversation between Southgate and U21s boss Lee Carsley in the weeks ahead.
Sources suggest England are confident Mainoo wants to represent them and there is a desire to integrate him into the setup but he will only become ineligible for Ghana when he plays a competitive senior international and this year’s fixture list has complicated the situation.
One solution would be for Southgate to select Mainoo at Euro 2024 but that would be a huge call given he has only made 17 appearances at first-team level.
Southgate is also only able to name a 23-man squad — reduced from the 26-man groups used at the previous World Cup and Euros, originally increased due to COVID-19 concerns — which means less room for experimentation and a possible wait until the autumn for Mainoo to play competitively.
At present, Southgate favours Declan Rice, Jude Bellingham, Jordan Henderson, Kalvin Phillips and Conor Gallagher among others in the midfield positions. Trent Alexander-Arnold was also listed as a midfielder in England’s previous squad for games against North Macedonia and Malta.
Meanwhile, a source has told ESPN that Southgate is also considering recalling goalkeeper Jack Butland after reviving his career at Scottish side Rangers following a free transfer from Crystal Palace last summer.