The Kuwaiti parliament called upon Iran today "to seriously intervene to secure the safety of all passengers and crew" of a hijacked Kuwaiti jetliner in Tehran after a 3 1/2-hour, closed-door session as the two countries traded charges over who was responsible for the impasse.

In a statement strongly backing the government's hard line toward the hijackers, the parliament also appealed to the United Nations and other "friendly governments" to intervene and "so end the pain and suffering of all the hostages."

The Iranian government, meanwhile, appeared to be stepping up the pressure in its own fashion on the Kuwaiti government to yield to the hijackers' demands in seeking to shift the blame for the deadlock to the Kuwaitis. Iranian Foreign Minister Ali Akbar Velayati was quoted by Tehran radio as saying Iran had the ability to end the hijacking by military means "but that Kuwait had opposed this."

[Kuwaits foreign minister, Sabah Ahmed Sabah, sent Tehran a formal denial of Iran's claim that Kuwait had barred an assault on the plane, Reuter quoted the Kuwait News Agency as reporting.]

Earlier, Tehran radio said the hijackers, who have also threatened to kill three Kuwaiti diplomats on board, were still awaiting "a clear reply" from Kuwait regarding their demand for the release of 17 terrorists being held here but made no mention of any new deadline. The aircraft was seized Tuesday during a flight from Kuwait to Karachi, Pakistan, and diverted to Tehran's Mehrabad Airport.

Iranian President Ali Khamenei was quoted by Tehran radio as criticizing the Kuwaiti government for "not using all efforts for the peaceful settlement of this issue."

Meanwhile, the Kuwaiti government was reported today by western diplomatic sources to have mounted "a very major diplomatic campaign" to bring pressure on Tehran to intervene and end the hijacking.

The government continued its official silence over the hijackers' demands, but diplomatic sources said it was still refusing to give in to their main one for the release of the 17 terrorists, mostly Iraqi Shiites, convicted last March for carrying out a spate of bombings here, including two at the U.S. and French embassies, last December.

Nor have the Kuwaiti media met the hijackers' demand for publication of their statement Friday explaining the reasons for their operation and their demands in return for the release of more passengers.

The United States was reported to be coordinating closely with the Kuwaiti government over the handling of the crisis and to be backing strongly its hard-line stand toward the hijackers despite their threat to kill another American.

The U.S. Embassy here has set up its own 24-hour task force to deal with the crisis. A source at the embassy said the Americans were in touch with the Kuwaitis "every couple of hours" and called cooperation between the Kuwaiti and U.S. governments "excellent."

Since the start of the crisis Kuwait has issued just one formal statement saying it would only negotiate with the hijackers after they released all passengers.

During the past three days, it has contacted a number of Arab and Moslem leaders, including those of Syria, Algeria, Pakistan and Saudi Arabia, in an effort to bring diplomatic pressure on Tehran to end the hijacking. Syria announced today that it was sending a high-level mediator to Tehran.

Meanwhile, Mustafa Mir Salim, the Iranian official who has been serving as the main contact with the hijackers, said Iran had considered military action right from the start but that Kuwait had refused.

Salim also was quoted by Tehran radio as saying that Kuwait alone was responsible for ending the crisis.

Salim said contacts had been established between the hijackers and Kuwaiti authorities, "and they are fully aware of the nature of the demands."

He warned that if "biased propaganda" against Iran continued and Kuwait refused to take "the necessary measures," then "naturally in spite of the efforts of Iranian officials a swift solution will not be reached."

Kuwait has set up a special team of three ministers led by Interior Minister Nawaf Ahmed to deal with the hijacking and sent a senior Foreign Ministry delegation to Tehran to handle the negotiations.