A bitter dispute between Iran and Iraq compelled the 13 oil ministers of the Organization of Petroleum Exporting Countries to end a two-day meeting here without naming a new secretary general.

Both Iran and Iraq, neighboring OPEC members who have been fighting a war for nearly three years, have nominated candidates for the largely prestigious post since the term of Gabon's oil minister, Marc Nguema, ended on June 30.

But the prospect of a political battle at a time when OPEC is struggling to maintain control of a glutted world oil market caused the ministers to delay deciding on the appointment until they meet again later this year.

The sensitive task of choosing a new secretary general underscored the persistent rivalry within OPEC between Iran and the Arab states of the Persian Gulf, led by Saudi Arabia.

Iran claims that its candidate, Hassan Kheradman, deserves the job because OPEC's charter calls for alphabetical rotation among founding members. In that case, it would be Iran's turn.

But Saudi Arabia, Kuwait and other gulf states fear that Tehran would exploit the post as a forum to denounce the conservative sheikdoms and promote its Islamic revolutionary views.

The Saudis and their allies have backed Iraq's candidate, Ramzi Salman, claiming that his respected background as a member of OPEC's board of governors would lend more prestige to the secretariat.

Saudi Arabian Oil Minister Ahmed Zaki Yamani argued that since all founding members have now occupied the post since OPEC was formed in 1960, the rotation system should be dropped to develop a more professional staff at OPEC's headquarters in Vienna.

The current impasse, however, is said to be acceptable to the Saudis because OPEC's deputy secretary general, Fadhil Chalabi, an Iraqi and a highly regarded energy expert who is close to Yamani, will serve in the top post until a successor is approved.

The OPEC members also agreed that Chalabi's work will be "supervised" by the new chairman of OPEC's oil ministers, Mana Said Otaiba of the United Arab Emirates.

Otaiba is expected to strive to protect the interests of Arab states of the Persian Gulf as OPEC girds itself for new difficulties in dividing up an oil market saturated by non-OPEC producers such as Britain, Norway, Mexico and the Soviet Union.

At a press conference after today's meeting, Otaiba said confidently that "we will take care of the stability of the market and will not rush into raising prices."

But OPEC's clout on the global oil market has severely diminshed as outside countries step up production.

In 1979, when OPEC increased prices from $18 to $34 a barrel, the 13 members of the cartel were producing 31 million barrels a day or about 65 percent of world production.

Today, OPEC's total output has plummeted to little more than 17 million barrels--35 percent of the world market.

One oil minister who declined to be identified said that Yamani, who has been placed in charge of developing a long-term strategy, told the OPEC meeting today that "serious changes were taking place and life may never be the same" after the boom era of the 1970s.

The growth in non-OPEC sources of oil has meant that the organization has become less influential in dictating the price of oil by calibrating its production levels.

Nigerian Oil Minister Yahaya Dikko, in his farewell speech as outgoing chairman, warned that OPEC's power may be further eroded if non-OPEC suppliers are allowed to seize the lion's share of additional oil sales once an economic recovery gathers momentum. "If OPEC maintains its existing quota, we may simply be allowing non-OPEC countries to capture this incremental demand and thereby reduce us to residual suppliers," he said.

In addition, OPEC's unity has been buffeted by the fact that several members borrowed huge sums to pay for vast development projects and were caught short of cash by the drop in oil consumption caused by the global recession.