Sen. Hubert H. Humphrey (D-Minn.) said today he wants to return to Washington in September to resume a vigorous role in government despite an inoperable cancerous tumor that stretches across his pelvis. His declaration was relayed to reporters through a hospital spokesman.

Fred Gates, a special assistant in Humphrey's Minneapolis office, said Humphrey meant "right after Labor Day - Sept. 5. Gates also said Humphrey had given no thought to resigning.

Meanwhile, among the calls that have flooded the switchboard of the University of Minnesota Hospitals was one from former President Nixon in San Clemente - but Humphrey napped most of the day and did not return any calls, including the one from Nixon.

President Carter talked to Humphrey prior to the operation Thursday and a large bouquet of red roses arrived from Henry and Nancy Kissinger. The family has, however, suggested contributions to the University Cancer Research Fund in lieu of flowers.

The hospital statement said Humphrey's doctors could see no reason why he couldn't carry out his plans.

In its bulletin this afternoon on Humphrey's condition after his colostomy operation yesterday, the hospital said the 66-year-old senator "indicated his intention to return to Washington after Labor Day to vigorously pursue those matters which are of vital interest both to Minnesota and to the nation."

Humphrey also said, according to this statement, that there is "A great deal of unfinished business and he will be in Washington to play an important role in completing it."

Eariler today Dr. John Najarian the surgeon who operated on Humphrey yesterday, said the senator was up and is "on his way to a superb recovery."

In a late afternoon bulletin, Dr. Najarian said Humphrey had a slight fever, slight lung congestion and was being fed intravenoulsy but said that all this was typical after surgery. He said that Humphrey might be given food by Sunday, but more likely on Monday.

Najarian, chief of surgery at the university's Hospitals, said Humphrey had an "excellent night and required very little pain medication." He reported that his patient insisted on weighing himself without assistance and that his "vital signs are strong." The doctor also said Humphrey's "physical findings are all normal."

The hospitals' spokesman did not know whether the call from San Clemente was repeated but said the switchboard had reported that it had come from a male member of President Nixon. Rosalynn Carter and Joan Mondale both called Muriel Humphrey, and it was reported that former President Ford, and Sens. Edward M. Kennedy (D-Mass.) and Charles H. Percy (R-Ill.) were among those who had called [TEXT OMITTED FROM SOURCE]