The legal team had initially set a Friday deadline.
"The ball is on their court, we've been waiting for their response," said Viana, a partner at law firm Vieira Rezende Advogados.
His lawyers want Hamilton, who was racing for McLaren at the time to support the claims.
He is an honorary Brazilian citizen and very well liked by Brazilians, so I hope he will support us," Viana said.
Despite that, Viana said Massa's legal team were confident they had a strong case and enough evidence to bring the Brazilian the championship.
Persons:
Felipe Massa, Lewis Hamilton, Bernardo Viana, we've, Viana, Vieira Rezende Advogados, Hamilton, Nelson Piquet Jr, Massa, Piquet, Fernando Alonso, supremo Bernie Ecclestone, Max Mosley, Mosley, Ecclestone, Charlie Whiting, Massa's, Nick de Marco, Gabriel Araujo, Ken Ferris, Toby Davis
Organizations:
SAO PAULO, Reuters, Formula, FIA, Ferrari, Massa, Renault, Singapore, Prix, McLaren, Hamilton, Mercedes, supremo, Thomson
Locations:
Singapore, Brazilian