The main opposition party in the Democratic Republic of Congo has reversed its decision to boycott the first full elections in four decades.
Tshisekedi has long opposed governments in Kinshasa
Etienne Tshisekedi said that his Union for Democracy and Social Progress (UDPS) would after all take part in the polls due by July 2006.
They had called for a boycott of a referendum two weeks ago in which a big majority backed a new constitution.
The UDPS said the West had unfairly supported those backing a "yes" vote.
Mr Tshisekedi once served as prime minister - and led the political opposition to former dictator Mobutu Sese Seko during his long reign.
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Presidential age limit reduced from 35 to 33
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Provinces increased from 10 to 26
Same-sex marriage banned
The UDPS is probably the best organised of the numerous political parties in the war-ravaged country.
"The UDPS, faced with its responsibilities before God and before history, undertakes to lead the Congolese people desirous of peace and change to the final victory in the coming elections," Mr Tshisekedi told reporters in Kinshasa.
Religious and foreign election observers said the referendum had been largely free, fair and transparent.
However, "No" campaigners are appealing to the Supreme Court to annul the vote.