American Express, the "don't leave home without it" credit card company, has told D.C. Mayor Marion Barry to leave it at home. And that goes for City Administrator Thomas M. Downs, too.

City officials confirmed yesterday that in late October American Express, citing repeated late payments, suspended a District government account used by both Barry and Downs. Barry was last allowed to use the card on a recent trip to Ottawa.

Barry's press secretary John C. White said the most recent late payments, overdue in an amount just over $1,000, occurred because Barry had instituted more stringent accounting procedures. "Because of this, it has taken longer in some cases to certify and verify the bills as they have come in," said White, adding that the review takes longer than the 30-day period allowed by American Express.

White said Barry plans to cancel the American Express account and open a new account with a bank card company, such as MasterCard or Visa, that allows partial monthly payments rather than payments in full.

City officials said the overdue American Express government account has since been paid.

Barry apparently intends to retain a separate personal card with American Express that was not affected by the government account.