The State Department is proud of its diplomatic tradition. But yesterday, an official who has spent five months wrestling with the hostage crisis finally exploded in a tense meeting with Iranian officials here.

"Bullshit," he said, in countering an Iranian allegation that the hostages were being protected by the Iranian government.

The expletive broke up a meeting at the State Department in which the Iranians were supposed to have received formal orders expelling all 35 diplomats from this country.

Shortly before President Carter's public announcement of the expulsion, Iranian charge d'affaires Ali Agah had been called to the State Department to receive those orders. Accompanying him was another Iranian official, Mohammed Lavassani. The two met with Deputy Secretary of State Warren Christopher and Henry Frecht, director of the office of Iranian Affairs at State.

The Iranians, however stormed out of the meeting early refusing to receive the official orders at the meeting and claiming that Precht had "cursed, insulted and used bad words" toward Lavassani during the session.

Agah, visibly angry, later told reporters outside the Iranian embassy: "We will not take any longer to have any of my brothers to be insulted."

Precht, reached by telephone, said that during the meeting both Iranians had been extremely critical of the United States, accusing this country of oppressing Iran and other people of the Third World. "They were saying that some of the hostages would prefer to remain in Iran. A certain tension was in the conversation," Precht explained.

Precht reminded them that the Iranian government at an early stage in the crisis had sent the United States a note that the government would assume responsibility for protecting the hostages. Precht then expressed dismay that such protection had not worked out.

Lavassani, according to Precht, then said the hostages "are being protected by the government, provoking Precht's one-word outburst.

Later, Agah told reporters outside the Iranian embassy that Iran would comply with the U.S. orders to leave. But, clearly angry from the exchange at State, he said, "The U.S. government does not understand us. They do not understand our revolution. They use language that I am ashamed of. The revolution gave us dignity and by insulting us they are trying to take our dignity away."

Iranian press attache Hossein Ava said the loss of communications between the two governments is "not going to help either Iran or the U.S. Any line of communication could benefit the hostage situation."