UNITED NATIONS, AUG. 11 -- Iran, in its first formal reaction to a United Nations Security Council resolution demanding a cease-fire in the Persian Gulf war, has delivered a blistering denunciation of the Security Council and the United States, U.N. officials said today.

A letter from Iranian Foreign Minister Ali Akbar Velayati to U.N. Secretary General Javier Perez de Cuellar was so bitter that the Secretary General persuaded Iran's U.N. ambassador, who delivered the letter yesterday, to replace the cover note with a shorter, less acerbic version, U.N. officials said.

Velayati's letter charged that the United States had imposed its will on the Security Council in an attempt by the Reagan administration to regain credibility with its allies and the American people after the Iran-contra scandal. It said it was a "disgrace" that the council had become a conduit of the United States.

The U.N. resolution, the letter said, "precludes the council from the possibility of constructive engagement" in the Iran-Iraq war and "makes more difficult all positive international efforts for a just resolution."

Velayati called the resolution an "illogical, unbalanced and impractical package."

The Velayati letter contained a five-page annex of specific Iranian objections to the resolution, including a charge that the council had become "a party to the conflict."

After meeting with Perez de Cuellar today, Iranian Ambassador to the United Nations, Said Rajaie-Khorassani told reporters that, in Velayati's letter, "we do not reject the resolution, we simply comment on its content." He added, "We will cooperate with the secretary general."

The Iranians held out hopes for a meeting between the secretary general and Deputy Foreign Minister Mohammed Jawad Larijani, who is due in New York Aug. 21 to attend a U.N. disarmament conference.

The Iranian response came after Perez de Cuellar convened a private meeting of the 15 council members this morning to report on his efforts and make clear that, as far as he was concerned, further action by the council would be required before Iran would accept a cease-fire in the seven-year-old conflict.

"I have asked the council for guidance, not for more time," Perez de Cuellar said.

U.S. officials conceded today that other Security Council members were not ready to consider imposing an arms embargo on Iran for its failure to honor the July 20 resolution.

Diplomats from several key council members -- including Japan, China, West Germany and the Soviet Union -- made clear their views that Iran must be given more time and that consideration of sanctions is premature.

U.S. officials, who have taken soundings in recent days, found few members ready to sit down and consider the text of a second resolution imposing an arms embargo.

Iraq has said it would honor the U.N. resolution as long as Iran would do so. Iraq on Monday bombed Iranian oil installations in the first Iraqi air attacks on Iran since the U.N. resolution.

Iraq said it resumed its raids because Iran had failed to respond positively to the demand for a cease-fire.