The Kinshasa government announced yesterday that it would allow UN peacekeepers to deploy freely with immediate effect, following its earlier rejection.
Authorisation came in a letter given to the UN mission to the Democratic Republic of the Congo (MONUC) by one of President Laurent Kabila's officials.
Mr Leonard Ntuaremba said the letter confirmed "the will of the government to see the UN forces deployed in Democratic Republic of the Congo".
Several dozen UN observers have been deployed in rebel areas since late last year in a bid to end the fighting.
The UN Security Council approved the deployment of 500 military observers and 5,000 support troops but have been unable to deploy them throughout the country, in part because President Kabila had refused to allow them to operate in areas under government control.
"Now we can restart our necessary preparations so that the deployment can take place as soon as possible," said the UN's Special Representative in Congo, Mr Kamel Morjane.
Rebels backed by Rwanda, Uganda and Burundi have been fighting the government since August 1998 and control large parts of the east and north of the country. Zimbabwe, Angola and Namibia are backing President Kabila.
A ceasefire was agreed in the Zambian capital, Lusaka, in July 1999, but it has not been respected by any of the parties.
Mr Morjane said there were no longer any restrictions on the movements of UN observers at Mbandaka or Kananga. He said there also was no objection to stationing an armed unit in Kinshasa to support the headquarters of the UN observer mission.
The Congolese Human Rights Minister said they had decided to suspend implementation of the Lusaka accord because circumstances had changed since it was signed in 1999.
Congo now wants to have fresh, direct talks with Rwanda, Uganda and Burundi. Rwanda rejected that yesterday, with the Foreign Minister, Mr Andre Bumaya, saying the Lusaka accord was the only way forward.
Mr Morjane said the government decision on the Lusaka agreement would not affect the UN deployment.
He said that if the UN Secretary-General, Mr Kofi Annan, judged conditions were right, "I think that we can go ahead with the deployment, even if the Lusaka peace process may have some problems in other areas".
In Washington, the US State Department said it was seeking clarification of the Kinshasa government's position in light of the apparent contradiction between the minister's remarks and the letter to the UN.
The US has repeatedly accused President Kabila's government of failing to live up to the commitments it made in the Lusaka agreement.