Saints are expected to do further business in the transfer window before it closes on Friday night.
They could bring a deal to sign Genk attacker Joseph Paintsil back to life, but defence is also an area Russell Martin wants to boost.
Southampton got in touch with Manchester City on Wednesday to push for a loan move for defender Harwood-Bellis.
They are continuing to work on it and hope it can be done by Thursday evening.
Harwood-Bellis was on loan in the Championship last season at Burnley and featured heavily in a Vincent Kompany side that won promotion.
Landing him would be a coup for Saints and a boost to their hopes of an immediate return to the Premier League.
The 21-year-old has also had loan stints at Blackburn Rovers, Anderlecht and Stoke City.