The 32-year-old striker is available on a free transfer after leaving Fulham and has already held talks at Leeds over a move to Elland Road.
Hayles, like Julian Joachim, is a proven striker at first division level scoring 19 times during the 2000/01 season when Fulham won promotion to the Premiership.
Hayles is believed to have received a number of offers from other clubs, and United's assistant boss Sam Ellis admitted: "It seems to have gone a little bit quiet at the moment."