The striker is not expected to be considered for selection against Finland and San Marino, despite Tottenham forward Harry Kane pulling out through injury, as he continues his bid to regain full fitness after a lengthy spell on the sidelines.
Keane has performed well for United's Reserves and Under-21s but was forced off the field after only a few minutes against Stoke City on Friday due to a head wound.
"I’ve invited Will along to join us for training this week and it’s great to see him back," Southgate told TheFA.com. "He suffered the injury when he was playing for England last year, so I’d like him to feel that he’s in our thoughts.
"He’s back playing for United now, so if this can help him in his rehab and help him get re-acquainted with his England squad mates then we’re more than happy to help."
Keane, whose twin brother Michael is also in the squad, revealed to ManUtd.com that he was in Southgate's thoughts during the previous international break.
"England got in touch with the club for the last games and asked about me but, at that point, United wanted me to focus on being here and getting the work out of the training," he stated. "Which is fully understandable.