The 31-year-old striker signed a two-year deal with the option of a third after passing a medical in London yesterday as the Magpies moved swiftly to complete the formalities.

Viduka, who has also been courted by West Ham, Portsmouth and Birmingham, rejected the offer of a contract extension at Middlesbrough to seek a new challenge on Tyneside.

He admitted that was a tough decision, but what Allardyce told him persuaded him it was the right one.

He told the club's website, www.nufc.co.uk: "Talking to Sam was a big turning point for me.

"I really wanted to hear what Sam's plans were for the new season and what players he was looking to bring in, and his answers matched with what I was thinking myself.

"I want to win things and Newcastle United is a club that has all the ingredients to do that, especially with Sam coming in.

"The potential here is enormous and I am really pleased to be part of it.

"It is definitely one of the biggest clubs in the country and if we can get success, then it will be something special."

Viduka's arrival came on a busy day for Newcastle as they awaited the completion of Joey Barton's £5.5million move from Manchester City.

The 24-year-old agreed the deal earlier this week and it is now just a matter of resolving one remaining administrative issue.

That would represent a major breakthrough for Allardyce, who identified the two men as his top targets for the summer.

Scott Parker's £7million transfer to West Ham means he has done his first two pieces of business for no extra outlay.

Allardyce will now turn his attention to Newcastle's much-maligned defence, with out-of-contract Bolton defender Tal Ben Haim a potential signing.

"To target some defenders is obviously key now," Allardyce told Sky Sports News. "We need to strengthen the back four for the start of the new season.

"Strengthening the defence will be my key area."

Allardyce's initial forays into the transfer market have been greeted warmly by the club's fans.

Mark Jensen, editor of fanzine The Mag, said: "When you hear what Middlesbrough fans are saying about Viduka coming to Newcastle, it says a lot about him as a player.

"He was the difference between them finishing in a respectable position in the table instead of really struggling in a relegation battle, and they are not happy at all about him leaving.

"When you compare it to last season when in Antoine Sibierski, we took a player Manchester City no longer wanted, this season, we have taken Manchester City's best player and pretty well Middlesbrough's best player.

"That is what we have to aim for, to be taking the best players away from other teams. That is how you are going to improve."

Billionaire Mike Ashley's proposed £134.4million takeover had earlier moved a step closer when he reached agreement to buy chairman Freddy Shepherd's stake at a cost of more than £37million, and the supporters will hope that could result in a huge cash injection.