Sir Bobby Robson last night refused to comment on his future after chairman Freddy Shepherd set the clock ticking on his Newcastle career.

Robson's side continued their pre-season preparations with a 1-0 defeat to Sporting Lisbon in the final of the Newcastle Gateshead Cup, but the major talking point at St James' Park was not Ricardo Tella's winner for the Portuguese side or the long-awaited debut of Patrick Kluivert.

Instead, all attention focused on the increasingly fragile relationship between 71-year-old Robson and his frustrated boss.

The pair were looking increasingly distant towards the end of last season as Shepherd bemoaned Newcastle's fifth-place finish and their failure to qualify for the Champions League.

And now the United chairman has publicly confirmed that Robson will not be retained as Newcastle manager when his contract expires in May.

Robson swapped his rolling one-year contract last season for a fixed-term deal that runs to the end of the forthcoming campaign.

That move was widely seen as paving the way for him to step aside, but it was expected that he would leave open the possibility of remaining at St James' Park.

Shepherd has previously steered clear of putting a time scale on Robson's reign but, when asked if there was any chance of Robson being in charge beyond the end of the season this weekend, he replied "No".

"Sir Bobby Robson's contract expires at the end of the season," added Shepherd. "We have no plans to extend that arrangement.

"Sir Bobby has given the club great service and we fervently hope he can bow out with a trophy. But this is his sixth season at the club and we have to look to the future."

Shepherd also stressed that Newcastle could not afford any more expensive mistakes in the transfer market, offering a thinly-veiled condemnation of some of Robson's less successful recent purchases.

"We have always backed the manager, we have been big spenders," he said. "But now we have got to make sure we get value for money - that's a nice way of putting it.

"(Carl) Cort didn't make it, (Hugo) Viana didn't make it, (Christian) Bassedas didn't make it. There comes a point where you say 'That's enough - we must have value for money'. We're not going to be anyone's mugs any more."

Hardly the ideal environment in which to prepare for a Premiership campaign, but Robson insisted that he was not aware of his chairman's remarks and therefore could not comment on them.

"I'm unaware of anything that's been written about me in the newspapers or said about me on the radio so it would be inappropriate for me to react," he said.

He will surely be aware of what has been said now and, with the start of the new season just 12 days away, will also know that he has just one more chance to win silverware with his beloved Magpies.

Robson can be expected to hold talks with his chairman in the coming days.

Shepherd's comments have prevented the inevitable 'Will he or won't he' clamour that would otherwise have plagued the second half of the season, but they have created a sense of transition that could yet jeopardise the club's hopes.

Manchester United's fortunes took a severe nose-dive when Sir Alex Ferguson announced that he would be leaving Old Trafford and Robson will be desperate to prevent the next nine months turning into a slow countdown to his departure.

Alan Shearer's impending retirement has already turned this season into something of the end of an era and, with Robson also leaving in May, there is now a danger of minds becoming distracted.

As if the public discussions over his future weren't bad enough, Robson is also having to cope with an injury crisis that threatens to hamper his side's start to the season.

Jonathan Woodgate is still to make his pre-season bow and, while the United boss insisted he had a "much better than 50-50 chance" of facing his hometown team on August 14, it is unlikely he will be fully match fit for the trip to Middlesbrough.

Jermaine Jenas continues to struggle with a thigh injury, while Craig Bellamy is still not fully recovered from his tendonitis, although he will play against Celtic at Parkhead on Wednesday night.

Shay Given and Andy O'Brien have both been laid low with an eye infection, while Laurent Robert and Darren Ambrose were unable to face Sporting after hobbling out of Saturday's win over Rangers.

"I'm not sure how bad things are with those two," admitted Robson. "Shola's (Ameobi) also got a bad back but I told him that he had to play.

"I also wanted to play Patrick Kluivert and Nicky Butt even though they're still a bit off being fully fit.

"They were never going to electrify the crowd because they've only been here a few days.

"Kluivert is in good shape. We need to be careful with him but it's not going to be too long until he's ready.

"I thought the whole side looked a bit sluggish to be honest.

"But we had a hectic match against Rangers on Saturday that went off like a bomb and finished like a bomb.

"That took a lot out of my players and I think it showed against Sporting Lisbon. But I'm sure things will fall into place.