Riordan is thought to be restless at Celtic Park (Getty)

Leeds United are unwilling to pay Celtic's �1m asking price for once-capped Scotland striker Derek Riordan, BBC Radio Leeds understands.

United previously tried to bring the 25-year-old former Hibernian star to Elland Road on loan in January.

Riordan scored over 60 goals in three seasons at Easter Road but has made only 13 starts since switching to Glasgow giants Celtic two years ago.

Championship outfit Burnley are also believed to be after the forward.