The University of the District of Columbia, top-seeded in the South Atlantic region as it enters its first postseason basketball tournament ever, is bristling over rival Mount St. Mary's selection as host for first-round competition.

UDC Athletic Director Orby Moss thinks Mount St. Mary's won home court rights when it guaranteed $17,000 of the gate to the National Collegiate Athletic Association, which oversees the competition. UDC, which also applied to host the tournament, refused to make any guarantee.

"I think they (the NCAA) set a precedent that shouldn't be allowed, letting a school almost buy the right to host a tournament and the right to the home court advantage, which is even more important," Moss said yesterday. He said gate guarantees are unprecedented in tournament applications.

Mount St. Mary's plays Virginia State at home in Emmitsburg, Md., on Friday night when UDC faces Virginia Union there. The winners meet on the same floor Saturday for the South Atlantic regional title. The winner of that game goes on to the quarterfinals of the NCAA Division II national tournament.

The sequence of events that led to Mount St. Mary's selection is complex, but Moss is convinced that the money guarantee was the key factor. He said he was told as much by Bob Moorman, chairman of the NCAA's South Atlantic region.

Moss said in its application UDC projected proceeds of $18,000, assuming a full house both nights. He said Moorman called him last week to see if UDC was willing to guarantee that figure, and Moss said no.

"He said, 'Well, you know Mount St. Mary's is guaranteeing it,' " Moss said. Then on Sunday, after the NCAA made its choice, Moss said Moorman told him, "It all hinged on finances. The Mount guaranteed the money."

The NCAA uses tournament proceeds to pay expenses for traveling teams. Excess funds go into a kitty that is divided up among competitors after the final, with bigger shares to the more successful teams.

Moorman confirmed that the guarantee was important. "This is a business," he said. "We're trying to make as much money as we can and we felt, all things considered, that we were assured of making more at Mount St. Mary's than at UDC," he said yesterday.

But the issue distresses Moss, who said he was "told a week ago by Gerry Miles, director of men's championships for the NCAA, that a guarantee was not necessary. He said he even tried to persuade Mount St. Mary's it wasn't necessary because anything could happen--a snowstorm or whatever--and they would be out the money."

Miles agreed from NCAA headquarters in Shawnee Mission, Kan., that he had tried to dissuade Mount St. Mary's from making the guarantee. But when officials at the Mount declined to withdraw it, he said, "We couldn't force them to."

Miles said Moorman's request for a UDC guarantee was unfortunate. "I told him, 'Bob, I wish you hadn't done that because it appears we're trying to twist arms to get guarantees.' In fact, we're against guarantees."

Miles maintained the guarantee was not a factor in accepting Mount St. Mary's bid. He said the six NCAA commissioners from across the nation who made the decision, one of whom was Moorman, "knew Mount St. Mary's had hosted the tournament last year and had done a superb job. The two (Mount St. Mary's and UDC) budgets were very close. The committee's point was that it would be risky at UDC-- would they be able to get their estimated attendance of 5,480 (for the two days)? At Mount St. Mary's, with its solid program and tradition, realistically they probably will sell out."

Jim Phelan, Mount St. Mary's athletic director and head basketball coach, said the NCAA decision surprised him, since traditionally the higher-seeded team gets the edge if all other things are equal. Top-seeded UDC is ranked third in the nation and beat Mount St. Mary's in the regular season.

"The NCAA feeling apparently was that we've drawn well all year. They went with something proven rather than something untried. We've got a boarding school here. We can guarantee a sellout."

For Moss, that's not the whole reason. "We're the new kid on the block as far as the NCAA goes. We have to win to prove we're real," he said.

If UDC does win, the benefits will come quickly. Whoever triumphs at Emmitsburg becomes host for the national quarterfinals that follow.