Hart scheduled to undergo a Celtic medical on Tuesday with an eye to putting pen to paper on a three-year deal.
Rangers manager says he has 'really strong relationship' with Connor Goldson amid ongoing contract discussions.
The group C fixture was due to be played at the Global Energy Stadium on Sunday.
Tannadice club open their Premier Sports Cup campaign with a 1-0 win over league newcomers Kelty Hearts.
Kilmarnock were relegated following a play-off defeat to Dundee last month.
The 52-year-old former Scotland striker has signed a two-year-deal at the Championship side.
Mellon, whose United team finished ninth in the Scottish Premiership last season, previously spent four years with Tranmere.
Manager Tommy Wright was meeting with his squad on Tuesday.
Manager Tommy Wright revealed he discovered by text message that the midfielder had returned to France.
Rangers, Celtic, St Johnstone, Hibs and Aberdeen will be Scotland's entrants in European competition next season.
Pars missed out on promotion after being defeated by local rivals Raith in the Premiership play-offs.
Ibrox club says 'small minority behaved inappropriately and in a mannor not reflective of our support' in George Square.
Queen's Park part company with their title-winning manager to 'begin the long-term task of restructuring'.
Ian McCall's side going up as champions after thrashing promotion rivals Falkirk 5-0 at Firhill.
League One clash was scheduled to kick-off at 7pm but was delayed before eventually being postponed.
Patterson impressed the Ibrox boss during Rangers' 2-0 victory over Celtic in the Scottish Cup on Sunday.
Highland club say striker showed 'exemplary conduct' after he was issued with excessive misconduct charge by the SFA.
Rangers boss believes players will continue to receive racist abuse on social media unless there is government intervention.
Ibrox boss says supporters 'must stay safe' as Rangers prepare to travel across Glasgow to face Celtic next weekend.
Hampden hearing set for March 25 after Rangers boss confronted referee during win at Tony Macaroni Arena.