Fletcher, who moved to Sunderland from Wolverhampton Wanderers in the summer, has been in prolific form by netting five goals in four appearances for the Black Cats.
The 25-year-old is believed to have held talks with manager Craig Levein, who fell out with the striker over his availability for a friendly against Northern Ireland in February 2011 and Fletcher has not played for the national side since August 2010.
Meanwhile, United midfielder Fletcher could feature in Scotland's qualifiers against Wales and Belgium later this month after returning to the field for the former Premier League champions last week, despite dealing with a chronic bowel condition.
Goalkeepers: Matt Gilks, Allan McGregor, David Marshall
Defenders: Christophe Berra, Gary Caldwell, Daniel Fox, Grant Hanley, Alan Hutton, Russell Martin, Charlie Mulgrew, Andy Webster
Midfielders: Charlie Adam, Scott Brown, Darren Fletcher, James Forrest, James McArthur, Shaun Maloney, James Morrison, Steven Naismith, Matt Phillips, Robert Snodgrass
Forwards: Steven Fletcher, Jamie Mackie, Kenny Miller, Jordan Rhodes