Manchester United have registered an interest with Southampton about the signing of defender Nathaniel Clyne, a source told ESPN FC.

United have been widely linked with a move to sign Clyne for several months, with the 23-year-old England full-back refusing to commit himself to a new contract with Southampton while he ponders his future at the club.

With his current contract set to expire in the summer of 2016, Southampton boss Ronald Koeman confirmed on Thursday that he has given Clyne 10 days to make a decision on whether he wishes to remain with the south coast club.

"I've spoken to Clyney, he's very happy and of course there is some interest but nobody has really bid for the player," Koeman said.

Yet a source said later on Thursday that Clyne is "fully aware" of the interest United have expressed in him and he will inform the south coast club of his future ambitions over the next few days.

Nathaniel Clyne says he's looking to play Champions League football sooner rather than later. Steve Bardens/Getty Images

Lines of communication between Southampton and United over Clyne have been open for "several weeks," but no formal bid has yet been made by the Old Trafford club for the latest star name to fall off the production line at Southampton.

Even though Clyne still has a year left on his contract, Southampton have informed United they have no interest in selling Clyne in a cut-price deal this summer and are prepared to hold on to the player if their asking price is not met.

Clyne confirmed earlier this month that he is keen to play Champions League football as soon as possible, and it remains to be seen whether the prospect of playing in the Europa League with Southampton next season will encourage him to stay with his current employer for another season.

Multiple reports have said United are eager to bring Clyne to Old Trafford, a year after they signed defender Luke Shaw from Southampton in a £27 million deal.