The Navy's top admiral has upheld disciplinary action against a senior officer found guilty of improprieties involving travel, forcing him to retire at lower rank, the service said Thursday.

Adm. Carlisle A.H. Trost, the chief of naval operations, "reviewed the case of Vice Adm. Kendall E. Moranville and approved the results of the flag mast (disciplinary hearing) . . . ," the Navy said in a statement released in response to a reporter's query."Under these circumstances, it would be inappropriate to nominate Vice Adm. Moranville for retirement in his present grade and therefore retirement was approved at the permanent grade of rear admiral, effective Oct. 1, 1988."

The Navy said Trost had conducted his review on Wednesday, studying an appeal filed by Moranville after he was disciplined with a punitive letter of reprimand last month.

In rejecting the appeal, Trost decided that Moranville would have to retire with the permanent two-star rank of rear admiral rather than the three-star rank he has held since June 1, 1985, the Navy said.

While there is almost no difference in pension between the two ranks for an officer with Moranville's tenure, Trost's action amounts to a permanent blemish for an officer of such high rank.

The Navy, which previously had declined comment on details of the case, disclosed Thursday that Moranville had been disciplined "for improprieties involving travel claims and the use of government aircraft."

Pentagon sources who demanded anonymity said the charges involved arrangements made by Moranville on behalf of a woman employed by the United Service Organizations while he was commander of the Navy's 6th Fleet in Naples, Italy.

Moranville, 56, stepped down from that post on Aug. 20 in a routine rotation and had been expected to assume a new post at the Pentagon until word of the disciplinary action surfaced.