An attempt by the 13-nation Organization of Petroleum Exporting Countries to agree on a long-term formula for regular, gradual oil-price rises appeared tonight to be mired in acrimonious dispute.

OPEC ministers ended two days of a conference called to adopt the formula by agreeing to meet an extra day, but some predicted that they would be no more successful Wednesday than they were today.

Oil Minister Mana Said Oteiba of the United Arab Emirates was the first to leave the session, saying, "There will be no agreement tonight. I doubt there will be agreement tomorrow. I'm going back to the hotel. I'm fed up."

Today's session of OPEC oil, finance and foreign ministers was marked by a sharp exchange of words between Iranian and Saudi representatives. There were signs that Iran in particular was becoming isolated within the organization, and that Saudi Arabia, OPEC's number one producer, was more determined than ever to use its weight to force adoption of a long-term strategy.

[OPEC ministers did agree, however, to open a dialogue with industrialized nations within the framework of the United Nations, United Press International reported. OPEC assistance to developing nations would also be discussed within this forum, conference sources said.]

Oteiba blamed the deadlock on the same three countries -- Iran, Libya and Algeria -- who have objected from the start to the formula worked out in two years of complex discussions by a committee headed by Saudi Arabian Petroleum Minister Ahmed Zaki Yamani.

Oteiba was soon followed out the door by Iran's deputy oil minister, Reza Azimi, who also predicted there would be no agreement on the long-term formula that Saudi Arabia has made a prerequisite for accepting the mounting pressure to raise its prices and lower its production.

Azimi blamed tonight's breakup first of all on Saudi Arabia, then on Iraq "number two and all the followers" -- referring to the 10 members of the organization that accept the Yamani formula.

It provides for phased price rises on a quarterly basis that are designed to double the dollar price of a barrel of oil over seven years until it reaches $60 -- OPEC's estimate of the equivalent price then for new forms of alternate energy, including the effects of inflation.

Even though the formula was accompanied by a number of escape clauses, the OPEC forecast that it would yield yearly price rises of 10 to 15 percent did not go fast enough, or far enough, for Iran.

Venezuelan Oil Minister Humberto Calderon Berti, who had said earlier in the day that his president would not attend the 20th anniversary summit meeting of OPEC in the Iraqi capital of Baghdad in November unless concrete decisions were adopted here, tried tonight to put the best possible face on things. He said the current meeting of OPEC ministers was not called to make decision but to make recommendations for the heads of state.

Iraqi Oil Minister Tayeh Abdul Karim said the Bagdad meeting would be useful "whether we get agreement here or not." Yamani refused to say anything at all to waiting reporters as he left Vienna's Hofburg Palace that has been the site of the conference for the past two days.

After the conference, the oil ministers are still scheduled to follow their original plan to meet separately on Wednesday to discuss current prices and production, even though agreement on that now also seems unlikely. The chief Iranian delegate predicted that the oil ministers would gather again in 10 to 15 days to dicuss those subjects, the only ones on which the Iranians seem anxious to seek an accord.

"We don't believe that without a short-term agreement that you can have a long-term agreement," said Iran's Azimi. The basic problem, he said, is the need to eliminate "overproduction."

The breakup after almost 12 hours of sessions today came despite what had looked like an Algerian-led attempt to work out a compromise whose final shape seemed to be clearly emerging. Some observers felt that such a compromise might nevertheless eventually take form, perhaps unofficially, if a way could be found to leave Iran aside.

Algeria proposed an amendment to the long-term formula that would leave any of the 13 OPEC members free to raise its prices any time those on the free, spot market went above certain limits.

Iran took the view that there is no real reason for any formula at all. "Why do we need predictability of prices?" asked an Iranian delegate. "Nobody gives us any predictability of prices of the things we buy."

Meanwhile, Libya, the third holdout, called on Saudi Arabia to reduce its production so that the current downward pressures on crude oil prices would be eliminated. A publicly distributed Libyan statement assailed "overproduction by some member countries beyond their real needs, which if not corrected, will seriously undermine the pricing structure of the organization."

While Saudi Arabia's Yamani admitted earlier that there is a current surplus in the international oil market, he made it clear that his country would not cut its current production of 9.5 million barrels a day until the organization has accepted his pet project to regularize price increases.

In a test of wills with Iran, the Saudis had given every indication earlier of being determined to underline the power they hold to control the oil market and thereby influence the oil revenues of other OPEC members. "Some countries who overpriced their oil will have to come down," said Saudi Foreign Minister Prince Saud Faisal.

Iranian polemics against the Saudis seemed only to increase their determination to make their weight felt. Conference sources said that a personal attack yesterday against Yamani as a "servant" of "imperialism" by Iran's Ali Akbar Moinfar had elicited a formal protest by Prince Saud. Moinfar accused Saudi Arabia of profiting from the production cutbacks caused by the Iranian revolution to the tune of $100 million a day.

There seemed to be sentiment developing to skirt OPEC's unaninimity rules and let Iran isolate itself, if that is what it wants.

Oteiba, the United Arab Emirates oil minister, said, "If one country doesn't like to join the majority, then that's okay."

Algeria's attempts to bridge the gap, no matter how much they appeared at first glance to gut the meaning of the long-term pricing approach, seemed to demonstrate the reality of the Saudi power position. The real effect of the Algerian amendment would depend on the price ranges and other conditions that are set for allowing members to ignore the formula, and that had appeared to be one of the main topics of negotiation this evening.

Libya had also said it hoped there would be a compromise, and even Moinfar appeared to be somewhat chastened today. "A full agreement is always impossible, but a compromise is possible," he said, adding at midday, "everything's fine. We're talking, talking, talking. Talking about talking."