NEWCASTLE United boss Bobby Robson yesterday warned he won't be held to ransom by Europe's star names.

Robson has endured a frustrating close-season, during which he has seen several targets slip through the transfer net.

Barcelona winger Boudewijn Zenden and Paris St Germain forward Laurent Robert are the latest to give Robson a headache as he attempts to add to the £6m signing of striker Craig Bellamy and free-transfer return of left-back Robbie Elliott.

Robson's ambitious moves are understood to have included enquiries about Emanuel Petit, before the Frenchman quit Barcelona for Chelsea, and Arsenal's Dennis Bergkamp.

Now Robson admits he has come up against a wall in pursuit of Dutch international Zenden and France star Robert, for whom United have offered £7m and £10m.

"There's no progress and it's disappointing,'' conceded Robson. "We've put good money on the table for two outstanding players without any success, but we'll continue trying.

"We are still attempting to strengthen a couple of positions. We've gone for big names for big money. I've been trying to sign Zenden for six or seven weeks, but he's not responding, which surprises me a bit.

"It's on hold now, although our info is he's looking to go somewhere - and they will sell. I gather they've had no financial offers apart from ours.

"It's frustrating, but we'll keep going. However, there will be a time when we'll tell them: If you don't want to come, we don't want you.

"A lot of other players would come to Newcastle.

"Zenden doesn't seem to be able to make up his mind what he wants to do, although his club have said they want him to go.

"With Robert, the problem is the agent. It wasn't a problem when you used to deal with the other club and the player.

"Now agents control the situation and we have to deal with them. He's holding it up and we won't get involved.

"If we went for another British player, there wouldn't be a problem. Not many of them would turn down Newcastle, but foreign players are tempted to go to London.''

An exasperated Robson is also looking to off-load one player in particular - £6m Spanish flop Marcelino.

The centre-back has been left out of the squad for the Intertoto Cup third round, first leg trip to Sporting Lokeren tomorrow. "I'm left with a lot of central defenders,'' said Robson. "There are five other centre-halves in the squad and I can't take another. He's come back and is working very well. He's enjoying his training and putting heart and soul into it as much as any player.

"He has to do it because he's fighting for his career and reputation. He's showing he's a good professional. We all thought that, by this time, he would have gone to a Spanish club.

"But it's a question of getting a Spanish club to have faith in him.

"He had injury problems last year, but finally got himself fit to play against Leeds, battled against Mark Viduka and came out on top.

"I was pleased with him and he showed he can play at that level.''

Meanwhile, Paraguay winger Diego Gavilan is in the United party which flies to Belgium today after being told he won't be released for the Copa America.

Robson said: "He stood still last year, but is stronger now. He's a talented player and should be okay. He has been playing for his country since the end of the season and has done very well. The Paraguay coach was imploring me to let him stay with them. I said my needs were greater than his.

"On the day he signed, Diego said he would give up international football. I said we would let him play when it was beneficial for him, but I've rejected the coach's pleas this time.''

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