CELTIC are likely to receive a firm 'hands-off' warning if they step up their interest in Middlesbrough's Gaizka Mendieta.

Sources in Scotland have suggested that Bhoys boss Martin O'Neill is interested in taking the Spaniard north of the border to compensate for the loss of star striker Henrik Larsson.

Larsson has told Celtic he will be leaving when his contract expires at the end of the season and now Mendieta has emerged as one of the men O'Neill is monitoring.

Boro signed Mendieta on a five-year deal in August, the first 12 months of which are a loan from Lazio, and they will fight off approaches from any interested parties.

Manager Steve McClaren's cause is aided by the fact that the attacking midfielder has already indicated he is more than pleased with the way things have gone during his maiden campaign in English football.

Mendieta recently said: "My first year in the Premiership has gone really well and we have already helped Middlesbrough win their first trophy (the Carling Cup).

"That means we will be playing in the UEFA Cup for the first time too and I am very happy."

While Celtic weigh-up their options, the cash dispute between two of Mendieta's former clubs rumbles on.

Primera Liga outfit Valencia, who sold the player for £29m in the summer of 2001, claim they are still owed around £10m of that huge fee from Lazio.

Both sides have opened talks centred on reaching an agreement and it is understood Lazio are willing to offer a number of their stars - reportedly Claudio Lopez and Simone Inzaghi - in a bid to finally sort out the wrangle.

McClaren, meanwhile, is continuing his search for a striker and his bid for Mark Viduka could hinge on whether Walter Samuel joins Chelsea.

The Blues have tabled a bid to Roma for Samuel, thought to be around £15m, and the Italian giants are likely to use some of that money to try to tempt Viduka to Serie A.

The Leeds striker is being sold, along with a number of others, to help ease the Elland Road club's debt following relegation from the Premiership.

And Leeds managing director David Richmond said: "Offers have been coming in from the very top clubs."

Meanwhile, McClaren has backed Newcastle United to reach the UEFA Cup final tonight and raise the profile of football in the North-East.

Boro became the first club from the region to lift major silverware in 31 years in February when they got their hands on the Carling Cup.

And Newcastle go into the UEFA Cup semi-final second leg at Marseille this evening looking to take a step closer to ending their own 35-year wait for major honours.

McClaren said: "The profile of this area has been projected on, with us winning the Carling Cup, Sunderland in the semi-final of the FA Cup and Newcastle in the semis of the UEFA Cup.

"It's fantastic for this area and it's certainly whet our appetite.

"Now we want Newcastle to go on because it's great for the area. The area has had a number of lean years but we have all got the taste for more."

Read more about Middlesbrough here.