The American Stock Exchange suspended trading in the shares of Auto-Train Corp. yesterday at the request of the Washington railroad.

Auto-Train said it asked to halt trading because of an announcement coming shortly, but company officials wouldn't discuss the nature of the announcement.

The railroad, which carries passengers and their cars from the Washington suburbs to Florida, reported a small profit for its last quarter of operations after several years of losses.

To pay off its past losses, the railroad has been trying for more than a year to raise money with a new stock offering.

Auto-Train faces a deadline of next Monday for getting additional financing, reports to the Securities and Exchange Commission show. The deadline was set by the Seaboard Coast Line Railroad, which owns most of the tracks used by Auto-Train and provides the engineers to drive its trains. Seaboard also has guaranteed payment of some of Auto-Train's debts.

Because of its financial problems, Auto-Train has been unable to pay for Seaboard's services on time, the reports to the SEC show.

Last fall, Auto-Train promised Seaboard it would get at least $3 million in new financing by March 31 of this year. On March 31, the deadline was extended to June 16.

Auto-Train executives could not be reached for comment yesterday on whether they will meet the Monday deadline. In March, Seaboard Vice President Richard Sanborn warned Auto-Train Chairman Eugene K. Garfield, "I must advise you that SCL does not contemplate further extending the deadlines."