EUROPEAN champions Liverpool are threatening to end any hopes Middlesbrough have of keeping Bolo Zenden on Teesside next season.

The Reds are believed to have already held preliminary talks with the Dutchman and the player has been left encouraged by negotiations.

It is a surprise move from Liverpool that could leave Boro searching for a new midfielder as they look to improve on last season's seventh-placed Premiership finish.

Zenden is out of contract at the Riverside Stadium and has turned down the club's offer - citing concerns over certain conditions and his agent and father, Pierre, went as far as to label it unacceptable.

Nevertheless, Boro chief executive Keith Lamb and manager Steve McClaren have both stated their confidence that an agreement can be reached.

But Liverpool's emergence as rivals for his signature look to be seriously casting doubt over Boro's claim for his signature.

Zenden has never been one to try to hide a desire to play at the highest possible level and has stated time after time that he would love to play in the Champions League again.

And, although Liverpool's place in the world elite club competition remains in doubt, their success in the competition in Istanbul last week makes them an attractive employer.

It was prior to the Anfield club's historic success in the Champions League final against AC Milan that first negotiations are understood to have taken place.

But nothing has been signed and a Bosman free signing to Liverpool is certainly not guaranteed to take place.

The fact that Zenden will cost nothing is appealing to Benitez, even though the Spanish boss does have millions to spend following the European Cup triumph.

PSV Eindhoven, the Holland international's first club, had previously explored the possibility of signing the 28-year-old but have realised they are not in a position to match his pay demands.

Since leaving PSV in 1998 he has gone on to play for Barcelona, Chelsea and Boro and all of those have been willing to pay him lucrative terms.

That is something PSV are unable to match and why Liverpool, armed with the cash they would save on a transfer fee, would be best positioned to land him.

Zenden, signed on a free transfer from Chelsea last summer, has become a fans' favourite in the North-East after scoring eight goals last season in Boro's push in the UEFA Cup and Premiership.

Meanwhile, Boro winger Stewart Downing will today have an exploratory operation on the injured knee that led to him withdrawing from the England squad.

Downing's problem could not have arrived at a worse time with so many big names out of the trip and debutant Kieran Richardson starred on the left side against the United States scoring two goals on Saturday.

The damage is not thought to be serious but a specialist will carry out an arthroscopic investigation today.

Manager Steve McClaren, Sven-Goran Eriksson's assistant in the States, remains hopeful that Downing will be back for the new campaign in August.

Read more about Middlesbrough here.