Sunderland boss Steve Bruce has been told to forget about trying to sign Wigan midfielder Lee Cattermole.

The Black Cats submitted a written offer for the 21-year-old this morning, but had it rejected within the hour as Latics boss Roberto Martinez left his predecessor in little doubt as to his feelings on the matter.

Martinez said: "Lee is not for sale. End of story. He is a fantastic player, a leader on and off the field, and is central to our plans going forward. We are not interested in selling him, which was why this offer was rejected immediately.

"It is not usually our style to discuss incoming or outgoing transfers until they are completed, but we have made an exception in this case because I feel so strongly about keeping Lee, along with all my best players. He is one of many talented players. Let's forget about this now and move on."

Just how keen Bruce is to recruit a man he took to Wigan from Middlesbrough last summer for £3.5 million will determine whether or not the Wearsiders test Martinez's resolve to hang on to him with an improved offer. However, all owner Ellis Short's financial backing will count for little if Sunderland cannot prise the England U-21 international from the Spaniard's grasp.

Lee is not for sale. End of story. He is a fantastic player, a leader on and off the field, and is central to our plans going forward.
Wigan manager Roberto Martinez

The Black Cats finally made their move after weeks of speculation they would bid for Cattermole, with some commentators suggesting they might have to go as high as £7million to land him. Bruce had been hopeful of making at least once significant addition to his squad before they head for Holland and the Amsterdam Tournament later this month.

While that man may not be Cattermole, it could be Manchester United striker Fraizer Campbell, also a target for Hull. It has been reported that the two clubs have agreed a fee for the 21-year-old which could eventually amount to in excess of £5million, and he will travel to the north-east for a medical and to discuss personal terms over the weekend.

That would represent a welcome breakthrough for Bruce and chairman Niall Quinn, who have been working all summer to identify targets. They have been heavily linked with a series of players, some of whom have since moved elsewhere - Didier Zokora and Jermaine Pennant among them - since the new manager's arrival.

Some of the speculation has been wild, but Sunderland have made an offer in the region of £11 million for Portsmouth striker Peter Crouch. AC Milan, Tottenham, Fulham and Blackburn have also been touted as possible destinations for the England international, who has reportedly grown unsettled at the ongoing uncertainty behind the scenes at Fratton Park.

Indeed, his agent, Jonathan Barnett, told the Portsmouth News: "He's a Portsmouth player, he likes the club and thinks a lot of [executive chairman] Peter Storrie and Paul Hart. He is happy, but if there are circumstances where he has to move, that is football, I'm afraid.

"He's still on holiday at the moment and has been given a few more days off by the club because he has been playing for England. If Portsmouth were to receive an offer from somebody, then we would have to listen to it."

Meanwhile, Spurs frontman Darren Bent remains in the Black Cats' sights, although the Londoners' valuation of a man for whom they paid £16.5million could be a stumbling block.