At the end of a confused day of intense negotiations about how much to raise world oil prices, the deadlocked Organization of Petroleum Exporting Companies decided tonight to extend its conference here another day in a last attempt to reach agreement.

The ministers of the oil cartel are sharply divided about selling a unified price structure and a ceiling on crude oil prices. If they fail to agree, oil prices could continue out of control in an upward spiral.

It seems certain that Saudi Arabia, the world's leading exporter and the foremost moderate member of OPEC, will raise its price from the present $14.55 to about $18. The others are expected to boost prices to an unexpectedly high range of about $20 to $23.50.

OPEC's current average price is about $18 for a barrel, which contains 42 gallons. The two poles of the price argument are represented by Saudi Arabia on the low side and radical Libya at the top.

Venezuela's new oil minister, Humberto Calderon-Berti, apparently worried about OPEC's future, said, "We cannot sustain the different prices because that is going to hurt OPEC."

The organization's main power has stemmed from its ability to impose a common price structure, but it has been unable to fill that role since the Iranian revolution brought chaos to the international oil market.

Calderon-Berti denied a statement made minutes before by Libyan Oil Minister Ezzedin Ali Mabruk that the 13 member states had agreed on a ceiling price of $23.50 a barrel and a basic price of about $20, with the Saudis holding their increase to about $18.

"We have a ceiling now," Mabruk had said to reporters in the lobby of the Intercontinental Hotel. "The ceiling is between $20 and $23.50."

The prospect was also raised that the West will not even get a breathing space at those high prices. The OPEC minister's have apparently agreed to meet in still another price-setting conference in three months.

Asked whether there would be another price meeting in September, Libya's Mabruk said, "Probably yes."

Until this year, the cartel has not increased oil prices in two successive quarters since the Arab oil embargo of 1973-74.

OPEC has raised prices more than 30 percent since this January. Another increase Thursday to $20 would make the total price rise nearly 45 percent in six months.

Following long morning and afternoon negotiating sessions, OPEC President Mana Saeed Otaiba of the United Arab Emirates called a meeting of the ministers without their aides in his hotel suite. But this did not produce an accord. Before the private meeting, Saudi Arabian Oil Minister Zaki Yamani said, "We are nearing conclusion, but we have no agreement."

After the meeting broke up, Kuwaiti oil minister Ali Khalifa Sabah told reporters, "There is an indication of an agreement; we haven't finished anything; beyond I cannot say."

The Saudis have sought to limit to about $1.50 a barrel the amount the exporting countries levy in extra charges for such factors as higher quality, low sulfur content and shorter distances to market.

Yamani, joined by the Venezuelans, the Emirates and a few others have even been suggesting that surcharges should be eliminated altogether.

The head of a major Middle Eastern delegation who asked not to be identified said that Yamani's threats about increasing production to force down prices are no longer taken seriously.

A member of the Venezuelan delegation said Yamani's power and prestige inside OPEC have eroded while others have gradually increased in stature among their fellow ministers. The inability of Yamani, whose country produces more than a third of OPEC's oil, to continue to impose his will on the organization appears to be an important factor in the cartel's disarray and the difficulty it is having in reestablishing its badly shaken unity. CAPTION: Picture, OPEC's current president, Mana Saeed Otaiba, left, of the United Arab Emirates, leaves a conference room in Geneva accompanied by Saudi Arabian Oil Minister Zaki Yamani and others attending the meeting to fix new oil prices. Copyright (c) Keystone, via Associated Press