A federal judge refused yesterday to dismiss bribery charges against former D.C. mayoral aide Joseph P. Yeldell and real estate developer Dominic F. Antonelli Jr., clearing the way for a trial of the two men to begin on Sept. 18.

However, U.S. District Judge Gerhard A. Gesell postponed his ruling on whether another charge against the two - conspiracy to defraud the District of Columbia of Yeldell's proper governmental functions - should be tried separately from the bribery counts.

The actions by Gesell came during arguments on preetrial motions filed by attorney Edward Bennett Williams for Antonelli and John A. Shorter for Yeldell. Both argued that the counts against their clients should be dismissed for various legal reasons.

The case centers on charges that Yeldell steered a city government lease to an Antonelli-owned building at 60 Florida Ave. NE in return for a $33,000 loan from Antonelli.

If Gesell rules that the conspiracy count must be tried separately from the bribery count, that conspiracy count would have to be tried in Superior Court because it is a local charge. However, it is most likely that the federal bribery counts would be tried in Gesell's federal court before any trial on the local conspiracy count.

The practical effect of any separation of the counts could be to limit the ease with which prosecutors could introduce evidence about actions taken by the two defendants during the alleged bribery scheme, some attorneys said yesterday.

Williams had asked that the conspiracy count be dismissed altogether on the ground that it was merely repetitious of the bribery counts, since it concerned the same scheme and the same acts.

He said that to allow both charges to be tried by the jury together would "be unfair to the defendants because it would give the government an evidentiary advantage."

Assistant U.S. Attorney Richard Beizer of the fraud division argued that any problems created by the two counts being tried together could be solved by special instructions to the jury by the judge.

He said the conspiracy count was charged because the "facts justify charging that count" and that it helped set forth the details of the alleged scheme with more clarity than would have been possible under a simple bribery count.

Gesell set another hearing in the case for July 27 to discuss pretrial preparations such as the possible sequestration of the jury for the September trial and the continuing exchange of documents between the prosecution and defense.