The D.C. Baseball Commission's drive to sell 10,000 season tickets by the end of July has passed the 50 percent mark during a week of above-average sales, according to Morris Siegel, consultant to the commission.

"We're over 50 percent there, and if we were a major league baseball team now, we'd rank 10th or 11th in total season tickets," Siegel said. The commission sold the equivalent of 573 season tickets from Sunday through yesterday, raising its total since April 17 to 5,343, worth $3,040,779.

The commission is asking people to open interest-bearing savings accounts of at least $70, with the money earmarked for the purchase of season tickets should Washington be awarded a major league franchise. An individual season ticket is $567 based on an 81-game home schedule, and there are less expensive plans available. The money can be withdrawn at any time, the commission said.

Siegel said the individual response has been "magnificent," but he is concerned that the business sector has been sluggish to respond.

"We're extremely happy with the individuals who have purchased tickets, but we would be much more gratified if the corporate and business community of Greater Washington would respond more," Siegel said. "This isn't a blanket indictment, but we're disappointed that there isn't a bigger response.

" . . . Some businesses have said, 'Count us in,' but we don't count them in until we get a receipt from the bank. But we're optimistic that we'll meet our goal by July 31."

The major league baseball owners will be meeting in August, and expansion is expected to be discussed.