The Central Intelligence Agency played an important role in the arrest in 1962 of Nelson Mandela, the African National Congress leader who was jailed for nearly 28 years before his release four months ago, a news report says.

The intelligence service, using an agent inside the African National Congress, provided South African security officials with precise information about Mr. Mandela's activities that enabled the police to arrest him, said the account by the Cox News Service.

The report, scheduled for publication on Sunday, quoted an unidentified retired official who said that a senior C.I.A. officer told him shortly after Mr. Mandela's arrest: ''We have turned Mandela over to the South African Security branch. We gave them every detail, what he would be wearing, the time of day, just where he would be.''

Mark Mansfield, a spokesman for the agency, declined to comment on the news-service report. ''As a matter of policy, we do not discuss allegations of intelligence activities,'' he said.