Mr Samakuva said Unita accepted the results despite its allegations of fraud
Angola's largest opposition party and former rebel group has said it accepts the results of last week's parliamentary elections.
With about 80% of votes counted, the ruling MPLA have 82% of the vote and Unita 10.5%, official results show.
Unita congratulated the Angolan people for their participation in the country's first elections for 16 years.
In the last polls, in 1992, Unita refused to accept defeat and resumed a long-running civil war.
Earlier, the electoral commission rejected a demand by Unita for the poll to be re-run in the capital Luanda, saying there was no evidence of alleged fraud.
The BBC's Louise Redvers says Unita's leader Isaias Samakuva made the declaration during a hastily arranged news conference on Monday night.
"Despite everything that happened, the Unita leadership accepts the election results and hopes the winning party, the MPLA, will govern in the interest of all Angolans," said Unita leader, Isaias Samakuva.
His spokesman added that the party wanted to congratulate the electorate.
"We thank in particular the electorate who voted for Unita and we are confident we'll represent you and your aspirations in the National Assembly," Unita spokesman Adalberto Costa Jnr said.
An MPLA spokesman has said that the results were in line with the expectations of the party.
Norberto dos Santos told the state-owned Jornal de Angola newspaper that the party's success was because of the dedication of their supporters.
"In every neighbourhood, in every village our supporters are there nearly every day like a priest at a Sunday service," he said.
The elections were seen as a crucial step in the country's recovery from decades of civil war.
Voting passed off peacefully on Friday but there were scenes of chaos in Luanda, and reports that more than 300 polling stations did not open or lacked materials.
Unita demanded a re-run in Luanda, but a commission spokesman said this request was turned down for lack of evidence.
In the lead-up to the election, Unita had accused the MPLA of intimidating its supporters and dominating state media.
The EU has said it would investigate claims by one observer of vote-rigging in Cabinda, but other observers have said the vote was transparent.
Our reporter says the head of the EU's observer mission stopped short of calling the elections "free and fair" and took an interpreter to task during a news conference when he used he used this phrase in a translation.
But Luisa Morgantini said the peaceful campaign had been an advance for democracy.
Some eight million voters are registered in the country - more than a quarter of whom live in the capital.
The MPLA has ruled Angola since the country gained independence from Portugal in 1975 but it fought a civil war against Unita until 2002.