A federal judge in New York yesterday denied a request by the special prosecutor investigating Hamilton Jordan to postpone the tax-evasion case sentencing of the Studio 54 disco owners who first charged that the White House chief of staff used cocaine at their club.

Sources familiar with the case said that U.S. District Court Judge Robert Owen rejected the plea by Arthur Christy in a closed session in his chambers.

Christy, appointed by a special court last fall to check the allegations against Jordan, apparently wanted to use the postponement to ensure the cooperation of club owners Ian Schrager and Steve Rubell by holding out the possibility that he would tell the judge of their aid.

The two pleaded guilty last fall to two felony tax-evasion charges that they skimmed hundreds of thousands of dollars in cash from the operation of the popular nightspot. They are scheduled to be sentenced Friday.

Their attorneys told prosecutors that Jordan used cocaine at the club in 1977. This was seen as an effort to trade their testimony against him for a reduction of charges in the unrelated tax case.

Attorney General Benjamin R. Civiletti recommended that a special prosecutor be appointed in the case, though a preliminary investigation didn't find enough evidence to support the charge. Civiletti did so, he said, because he felt that the new ethics-in-government law didn't give him the authority to grant immunities and use other legal tools needed to dismiss the charge.