Mount and James were included in the England squad for next month’s World Cup qualifier despite carrying injuries.
Southgate admits “there is an element of the unknown” over their availability for England against Andorra and Hungary next month, but he hopes they will be fit.
Speaking on Thursday, Southgate said: “Clearly they are still to appear for their clubs so there is an element of the unknown.
“Our understanding is that Mason and Reece have a good chance for the weekend [against Southampton]. We’ll have to track that.
“We don’t play until next Saturday so there is a bit of time and we will know more as the week progresses.”