The Public Broadcasting Service, unyielding in its decision to air a film vehemently protested by the Saudi Arabian government, yesterday found itself at odds with two of its major benefactors: Congress and the Mobil Oil Corp.

Mobil, a partner in oil with Saudi Arabia, bought ads in major newspapers urging PBS to "review" its decision in light of "what is in the best interest of the United States." Mobil gives more than $3 million annually to public broadcasting.

At the same time, two powerful members of Congress -- which also funds PBS -- registered objections to the film and urged that it not be shown Monday as scheduled. Rep. Clement Zablocki (D-Wis.) and Rep. William S. Broomfield (R-Mich.) accused PBS of using poor judgment in deciding to air the film.

Zablocki is chairman and Broomfield the ranking Republican on the House Foreign Affairs Committee.

The actions came as the State Department yesterday forwarded to PBS a formal letter of protest about the film -- "Death of a Princess" -- from the Saudi Arabian government.

The Saudi ambassador to the United States, in a public statement late yesterday, sounded a further ominous note in the controversy: "The timing of the showing of the film in the present period," the statement said, "makes clear it is part of the continuing and recently stepped-up effort to undermine the internationally significant relationship between the United States" and Saudi Arabia.

In the face of this barrage, a spokesman said PBS had no plans to change its mind. "We stand by the integrity of the broadcast and plan to air it as scheduled," the spokesman said.

Neither Mobil nor the two congressmen directly threatened PBS' funds. But the implications of the criticisms again raised questions about public broadcasting's financial structure and its potential vulnerability to pressure. b

"Death of a Princess" is a British-made drama about the 1977 execution of a Saudi Arabian princess and her lover for adultery. It was aired in Britain despite strong protests from Saudi Arabia that it was inaccurate, insulting and a slur on the entire Islamic community.

After it ran, Saudi Arabia began a full-scale review of its relations with Britian, recalled its ambassador and, yesterday informed British Airways that it could no longer land its Concorde supersonic plane in Saudi Arabia.

In a letter Wednesday to acting Secretary of State Warren Christopher, Saudi Ambassador Sheikh Faisal Alhegelan did not say what his government would do if PBS aired the film. The State Department nonetheless took the letter seriously, forwarding it quickly to PBS -- but including with it a statement disclaiming any attempt at censorship.

The United States "cannot and will not attempt to exercise any power of censorship over the Public Broadcasting Service," Christopher wrote Lawrence Grossman, PBS president. "We have no doubt that, in the exercise of your own programming judgment, you will give appropriate consideration to the sensitive religious and cultural issues involved and assure that viewers are given a full and balanced presentation."

At least 10 stations, including eight in South Carolina, have said they will not carry the program. It is not mandatory that local stations broadcast the PBS film.

Mobil's ads, the first of which ran in The New York Times yesterday, said the PBS decision "raises some very serious issues" about the "responsibilities and obligations" of the press.

The ads suggested that the film "demeans another nation's religion and possibly jeopardized U.S. relations" with Saudi Arabia. It did not mention its relations with the Mideast nation, which supplies massive amounts of oil to Mobil and other U.S. firms.

Mobil is a partner with those other firms and Saudi Arabia in Aramco, the giant that produces 75 percent of Saudi oil.

"Death of a Princess," the Mobil ads said, "is a new fairy tale. . . . We hope that the management of the Public Broadcasting Service, will review its decision to run this film and exercise responsible judgment in the light of what is in the best interest of the United States."

A Mobil spokesman said the ads were prepared independently by Mobil without "as far as I know" consultation with Saudi Arabia. The spokesman also said the corporation would not withdraw financial support from public broadcasting if "Death of a Princess" is aired.