The prolific 26-year-old was on Teesside at the weekend as Boro stepped up their pursuit of the Heerenveen player.

However, that angered AZ Alkmaar, who are convinced they have a pre-contract agreement with Alves.

They have now turned to the Dutch Football Association (KNVB) for a ruling and their decision and any subsequent legal wrangle could leave Boro facing a race against the clock to land their man before the January transfer window closes.

Alves now appears to be committed to playing his football outside Holland, but he could yet find himself on the books at AZ, an outcome which might leave the Teessiders back at square one.

AZ spokesman Klaas Wilting confirmed his club's stance in an official statement.

He said: "There is a signed transfer agreement between AZ and SC Heerenveen concerning a move from Afonso Alves to AZ.

"All parties involved have reached agreement about their share in the transfer fee to which Alves is entitled, according to his contract with Heerenveen.

"There is a signed employment agreement between AZ and Afonso Alves as from 1 January 2008.

"AZ and Alves have signed a transfer form meant for the KNVB. Heerenveen refuse to sign this form.

"Therefore AZ have filed an emergency arbitration at the KNVB, the Dutch FA, on Friday 11 January to see to it that Heerenveen will meet their obligations."

Boro insist they are considering a series of targets - they also have an interest in Lyon striker Fred - in case they meet dead ends with certain approaches.

However, they have made good progress with Alves, whom they believe they can land for around £10million rather than the £14.9million which has been suggested.

But AZ's position is a complication they could have done without.

Their pursuit of the Heerenveen man and his compatriot Fred is not necessarily an 'either-or' situation, although a double swoop could yet mean Tottenham's interest in Stewart Downing might come into the equation.

Boro have also been linked with a move for Portsmouth's Matt Taylor, and manager Gareth Southgate could do with a left-sided reinforcement after discovering that he will be without full-back Andrew Taylor for two months.

The 21-year-old was today due to undergo surgery on the tendons in his foot after being sidelined since November.

Taylor, and England Under-21 international, has been diagnosed as suffering from plantar fasciitis.

* BOLTON have signed Iceland international Gretar Steinsson for $8.5million from AZ Alkmaar.

BIRMINGHAM are set to complete their first signing of the January transfer window with Hibernian full-back David Murphy moving to St Andrews in a $3.7million deal. The club are also closing in on signing Everton striker James McFadden.

DERBY have revealed they have rejected another bid from Maccabi Tel Aviv for American midfielder Benny Feilhaber.

SPURS' interest in Fred is believed to have cooled, despite the Lyon striker's agent suggesting he will meet White Hart Lane officials on Thursday.

Branislav Ivanovic completed his dream move to CHELSEA on Wednesday after agreeing a three-and-a-half year deal with the English club.

PLYMOUTH have signed Scotland B international Chris Clark from Aberdeen for $500,000.

HAMBURG have signed midfielder Anton Putsilo on a year-long loan deal from Dinamo Minsk.

ARIS SALONIKA have completed the signing of Brazilian striker Marcio Amoroso on a free transfer.

RUBIN KAZAN have announced the signing of Argentinian defender Cristian Ansaldi from Newell's Old Boys.

Kandia Traore has completed his switch from Al Wasl to Ligue 1 strugglers SOCHAUX.

PSV Eindhoven director Jan Reker insists any offer from VALENCIA and their former coach Ronald Koeman for defender Carlos Salcido will go "directly into the litter bin".

HEERENVEEN look set to sell midfielder Michael Bradley at the end of the season.

REAL MADRID president Ramon Calderon insists he would not swap defender Sergio Ramos for FIFA World Player of the Year Kaka.

NEC have completed the signing of midfielder Bas Sibum from Roda JC for an undisclosed fee.