The Sun today reports that Glenn Roeder is interested in the former Bury, Oldham and Blackpool man, who can play at full back or further forward, but whom the Sun describe as a 'tough-tackling midfielder'.
The Mirror have also picked up the story, saying that a £900,000 bid for the 'tigerish midfielder' has taken Bryan Robson by surprise.
Armstrong has started 22 times for the Blades this season. he moved to Bramall Lane in 2003 for a £100,000 fee.