Middlesbrough cancelled his contract in January after an appeal against a positive test for the performance-enhancing steroid dianabol was rejected by UEFA.

"In no way do we condone the taking of drugs but the ban was reduced by the game's governing authorities, which suggests there was a significant reason for that," Boro manager Gareth Southgate said on the club's Web site on Wednesday.

"I'm a believer that people in life who serve a sentence should get the opportunity to rebuild their life or their career afterwards. He's served his ban and wants to force his way back into the side."

Mozambique-born Xavier, who joined Middlesbrough from AS Roma in August last year, became the first Premier League player to be banned for doping when he failed a test after a UEFA Cup tie against Xanthi the following month.

Originally banned for 18 months, his suspension was cut to 12 months by the Court of Arbitration for Sport in July.

Xavier has played 20 times for Portugal and had spells with Benfica, Bari, PSV Eindhoven, Everton and Liverpool.