Juninho: Back with Boro (CliveBrunskill/Allsport)

The Premiership outfit have been locked in talks with the 29-year-old after agreeing a £6million fee with his Spanish club Athletico Madrid earlier this month.

And following protracted negotiations, Middlesbrough announced they had finally come to an agreement with the midfielder.

A statement on the club's official website read: 'Middlesbrough Football Club are delighted to announce that last night they agreed personal terms with Juninho having already agreed a fee with Athletico Madrid.

'The club has agreed a four-year contract, subject to the player passing a medical and obtaining a work permit from the Department of Employment.

'The Brazilian international is due to link up with his new team-mates week commencing August 5 and it is hoped that he will make his debut in the pre-season friendly against Alaves on Wednesday, August 7.'

Boro boss Steve McClaren spoke of his delight at the capture. He said: 'I'm absolutely delighted Juninho has agreed to join us. We have a World Cup winner who is as ambitious as we are.

'I have spoken to him a couple of times and he wants to help make Middlesbrough successful. He is very excited to be coming back to Teesside and we look forward to welcoming here. He feels he has unfinished business.

'Juninho is the sort of player who can unlock tight defences and create goals, which is something we lacked last season. He will bring us that something extra that we have been missing.'

Juninho was a big hit during his previous two spells at the Riverside Stadium. He first arrived in England from Sao Paulo for £4.75million in November 1995 and set the Premier League alight with his electric runs.

Although Boro reached both the FA Cup and League Cup finals in 1997, the little Brazilian could not prevent the club from being relegated to Division One.

He was subsequently sold to Athletico Madrid for £12million, but returned to Middlesbrough on loan in September 1999 after failing to hold down a regular first-team place in Spain.

Juninho was then farmed out to Brazilian sides Flamengo and Vasco da Gama before catching the eye at this summer's World Cup finals in Japan and Korea.

Middlesbrough chief executive Keith Lamb has been relentless in his negotiations to bring the playmaker back to the club, holding length talks with Juninho's agent and father, Osvaldo Giroldo.

The Teessiders agreed a #6million fee with Atletico early this month, but could not agree personal terms when Giroldo flew to England. However, as he returned suggesting the World Cup winner would resume his career with Madrid next season, the Teessiders upped their offer, making it clear it was their best and final package.

And following more talks, the two parties have now come to an agreement which looks set to see Juninho boost McClaren's squad - although the deal remains subject to a medical and the Brazilian obtaining a work permit.

McClaren and his players are currently in Austria, where they drew 2-2 with Italian side Udinese in a pre-season friendly last night.

They flew out having clinched a season-long loan deal with Real Madrid's Cameroon international Geremi, who has had his application for a work permit approved.

Former Middlesbrough defender Gary Pallister believes Juninho can once again have a major impact at the north-east club.

He told Sky Sports News: 'When he first was at the Riverside, they had some good times and some of the football they were playing was superb. Now he is back to his best and we saw in the World Cup he is a superb player.

'He played exceptional well for three or four games and he looked like the Juninho of old. He spent two or three years where he has not been the same player because of this really bad injury when he broke his leg.