Chainho played for FC Porto in 2001
Angola want Fifa to allow Portugal-based players Pedro Emanuel and Chainho to change their international allegiance in time to play at the World Cup.
Angola FA vice-president Jose Luis Prata said he was travelling to Fifa headquarters in Zurich in a bid to gain permission for the two players to feature for the Palancas Negras in Germany.
Thirty-one-year-old Porto defender Emanuel, a former Portuguese under-21 international, has finally agreed to play for Angola after rejecting several previous offers from the country of his birth.
Angolan-born Chainho, also 31, represented Portugal at junior level, and is a midfielder with Maritimo.
He has previously played for Porto and top Greek club Panathinaikos.
Prata said Angola would be seeking the personal intervention of Fifa president Sepp Blatter.
Angola begin their World Cup campaign against Group D opponents Portugal in Cologne on 11 June.
Since January 2004, players with dual citizenship or nationality who have not played international football above under-23 level have been eligible to apply to change the country they represent.
But they must make the application before their 21st birthday, a rule which would appear to disqualify Emanuel and Chainho from turning out for Angola.
Emanuel was a member of the Porto side which won the 2003 Uefa Cup and the 2004 Champions League.
Angola have been keen to use him to bolster a defence which coach Luis Oliveira Goncalves said looked fragile and inexperienced at the African Nations Cup finals in Egypt earlier this year.
Last week, the Tunisian Football Federation said it was hoping Blatter would reverse an earlier Fifa decision to deny Toulouse midfielder Nabil Taider the chance to play for the north Africans at the World Cup.
The 22-year-old Taider won caps for France at junior level but qualifies for Tunisian citizenship through his parents.
Fifa turned down his application on the grounds his application was made after his 21st birthday.