De Sousa had been in Brazil along with Portugal’s prime minister, António Costa, for events to mark 10 June, the Day of Portugal, of national poet Luís Vaz de Camões and of Portuguese communities abroad.
“When Brazil and Portugal are added together, we are doubly invincible,” de Sousa said. “When we join together, we are really the best in the world.
“And when we join together with our brothers who speak the same language we are still better and we are greater,” he continued, at a reception on Sunday evening for the Portuguese community in the consulate-general in Rio de Janeiro - the last stop on the programme to mark Portugal Day.
The celebrations had begun on 10 June in Portugal - in Porto - before moving on to São Paulo and Rio de Janeiro on 11 June.
Despite de Sousa’s call for unity, he and Costa were not received by Brazil’s president, Michel Temer, during their visit.
On Saturday, the Portuguese president said that a meeting had been planned, at Temer’s request, but that it was subsequently cancelled due to an agenda clash.
Temer remains under fire after the emergence of a recording of his allegedly sanctioning the bribing of political officials. He has denied any wrongdoing and rejected calls for him to step down.
Earlier, Portugal’s prime minister and president inaugurated the new chancery building next to the Palácio de São Clemente, the Portuguese embassy, just as the giant statue of Christ the Redeemer, on Corcovado mountain, was lit up with the colours of the Portuguese flag in the background.