MADRID, July 6 (Reuters) - Atletico Madrid have signed Brazilian midfielder Paulo Assuncao as a free agent and are negotiating the sale of Portugal midfielder Maniche.

Assuncao, 28, used FIFA's Article 17 on transfer regulations to break out of his contract with Porto but Atletico are seeking to reach a 'friendly agreement' with the Portuguese champions, they said on their website.

Only available to players who have already served three years of their contract, or two years in the case of players aged 28 or over, article 17 effectively allows players to 'buy out' the remaining time on long-term contracts.

Atletico said fellow midfielder Maniche would not be joining up with the rest of the squad on July 7, as they continued negotiations with a number of clubs over a possible transfer.

Assuncao, who won three league titles in his three seasons with Porto, will join Czech Republic defender Tomas Ujfalusi, Netherlands defender John Heitinga, France goalkeeper Gregory Coupet and French striker Florent Sinama Pongolle as new recruits at the Calderon.

Atletico are in the third qualifying round of the Champions League after finishing fourth in the Primera Liga last season.