Three Washington men were indicted yesterday on conspiracy and cocaine distribution charges after they allegedly sold more than a kilogram of pure cocaine to an undercover agent during negotiations for the men to deliver to the agent a kilogram of pure cocaine a day.

Drug Enforcement Administration agent Emile Manara said in an affidavit filed in court that the cocaine tested as virtually pure and would have had a street value of about $500,000. Most cocaine sold on the streets is only 20 percent pure, according to the affidavit.

Sources said the men, two of whom are West Indians, are believed to be part of a major Jamaican drug network now operating in the city, and officials said they believe the men had the capability to deliver the large quantities of the drug.

The men were identified during a bond hearing yesterday as Barrington Green, 36, also known as Orlando Clemente; Calvin A. Powell, 34, of 66 New York Ave. NW, and Antonio J. White, 32, whose most recent address was 1513 Meridian Place NW. U.S. Magistrate Jean F. Dwyer ordered the three held without bond.

Assistant U.S. Attorney John Finnegan said that Green is wanted by New York authorities on a misdemeanor bench warrant, and that he allegedly fled New York in early 1986 after failing to report for sentencing after pleading guilty to selling drugs. Green has been living in the Washington area for 1 1/2 years and worked for a local car company, according to court records.

Powell has no prior criminal record as an civilian but is appealing a Marine court-martial on undisclosed charges, his attorney said during the hearing.

White has filed a civil suit in D.C. Superior Court against the D.C. police department as the result of an allegedly illegal raid on his house early last year, White's attorney, Nina Kraut, said during the hearing.

Manara testified in court that negotiations for the alleged cocaine deal took place during rush hour on a busy street corner in Northwest Washington last Thursday afternoon, almost within sight of the 4th Police District headquarters at 6001 Georgia Ave.

Manara testified that while he was meeting with White and Powell at Georgia Avenue and Piney Branch Road NW, Green repeatedly drove past the corner in a late model Mercedes-Benz 190.

During the meeting, while Manara, White and Powell were sitting in a DEA undecover car, Manara said, he showed the two men $30,000 in cash in his glove compartment and that Powell "counted every bill." But the men were not able to produce the drugs, despite making several calls on a telephone in Powell's own Mercedes-Benz, and the deal was reset for the next day, Manara testified.

Agents later followed Powell and Green as they drove in tandem, at times nearly colliding as each man talked on his car phone, for about 45 minutes, Manara said. Manara said he met Powell and White the next day at a Giant Food store at 14th and Meridian streets NW where a brick of slightly more than a kilogram of cocaine was delivered and the men were arrested.