USA Today, Gannett Co.'s national daily newspaper, will begin publication Sept. 15 with an edition serving Washington, Maryland, Virginia, Delaware and Pennsylvania.

Advertising rate cards also will be released next month, Gannett said. Circulation projection for the newspaper in the Washington area by the end of the year is 200,000. However, the company plans to expand into 10 more areas by the end of the first quarter of 1983, with total projected daily circulation by the end of next year of 1.2 million.

USA Today is planning to carry the same advertising and news content throughout the country except for updated news stories in West Coast papers. It will be printed at numerous plants. The newspaper's staff will be based in Rosslyn, and the paper will be designed and printed at the Army Times Publishing Co. plant in Springfield, where a satellite dish already is in place to transmit completed pages to other printing plants around the nation.

After Washington, the 14 metropolitan markets where USA Today will be circulated within the first six months are Baltimore, Atlanta, Chicago, Denver, Detroit, Houston, Los Angeles, Miami, Minneapolis-St. Paul, New York, Philadelphia, Pittsburgh, San Francisco and Seattle. Except for the San Francisco area and in Westchester County north of New York City, Gannett has no major daily operations in these initial markets.