Rafa Benitez has revealed for the first time that he cannot guarantee he will be in charge at Newcastle United at the end of the season.

The Newcastle manager’s contract at St James’ Park ends this summer and Benitez can walk away for nothing, with the penalty clause that would have seen him have to pay £6million now invalid.

He had refused any attempts at a renegotiation, including the possibility of a short-term one-year extension, until he'd seen how the club had strengthened in the current transfer window.

Newcastle have still to sign a single player, after an attempt to take the left-back Jordan Lukaku on loan broke down on Friday night, and when asked if he could guarantee he would not walk out before the end of the season, he replied: “No, I cannot guarantee anything.”

Benitez’s fraught relationship with the club owner Mike Ashley has once more been stretched to breaking point following another transfer window in which his attempts to bolster the Newcastle first team squad have been thwarted.

Ashley went into Benitez’s office at St James’ Park after a rare home victory against Cardiff earlier this month, but the Spaniard has admitted it was a fruitless visit, and that nothing has changed.

He has clashed with the club over recruitment for three of the last four transfer windows and had gagged himself from talking about the matter.

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However, with the window due to close on Thursday, he spoke of his own future and then refused the opportunity of advising supporters to renew their season tickets, with deadlines approaching.

“That is not my business,” he said. “My business is to prepare the team against Manchester City and be sure they can compete until the end of the season.”

Newcastle fans have already planned a series of demonstrations against Ashley at Tuesday’s televised Premier League game with Manchester City at St James’.

Supporters will be handed DW Sports leaflets to hold up in an attempt to antagonise the Sports Direct owner, and there is a plan for a sit-in demonstration when the game has finished.

Against that backdrop, Benitez spoke of his impromptu meeting with the owner. “It didn’t change anything,” he said. “You just have more ideas. It’s exactly the same position.

View photos Newcastle fans protest against Mike Ashley earlier this season(Getty) More

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