SAN FRANCISCO (AP) _ Shares of Gap Inc. plummeted more than 20 percent Thursday following a warning by the clothing retailer that second-quarter earnings would likely come in below Wall Street's expectations.

Citing sluggish sales in July, the San Francisco-based company said earnings per share likely will be 2 to 3 cents below the 23 cents estimated by analysts surveyed by First Call/Thomson Financial.

The warning came out after regular trading was finished Wednesday. In early trading Thursday, shares of the Gap fell $8, or 21 percent, to $29.938 on the New York Stock Exchange.

Gap officials issued the warning after getting ``weaker than expected results'' in July. Other major department store retailers nationwide have also been reporting slow summer sales.

Gap sales for the four weeks ended July 29 increased 22 percent to $851 million from the year-ago period. Same-store sales for July dropped 1 percent, however, compared to a 2 percent increase in July 1999.

The company said its domestic unit reported July sales growth in the low double digits; Banana Republic had flat growth; and Old Navy slipped.

Comparable store sales for the 26 weeks ended July 29 decreased 2 percent, the company said. It increased 10 percent in the year-ago period.