For the 13 nation Organization of Petroleum Exporting Countries, it was hardly the way it had hoped to wind up its 20th year as the most influential cartel of modern times.

The organization, which produces about half of the noncommunist world's petroleum, had planned to hold a 20th birthday summit party for itself this fall in Baghdad, Iraq, where OPEC was born. But the war between Iraq and Iran, two founding members, shelved that plan.

With Iraqi Mig21s bombing the Iranian capital of Tehran and Iranian F4 Phantoms striking at Iraqi refineries outside of Baghdad, the question of OPEC's very survival was one being raised not only in the chanceries of the world's industrial nations, but also in those of OPEC's own oil ministries.

"The question OPEC has had to face this year was not so much that of how it would continue to function to regulate the world's oil pricing," said Venezuelan Oil Minister Humberto Calderon Berti. "The key question we have had to confront was whether we could remain united."

The semiannual price-setting meeting of OPEC's oil ministers held here earlier last week confronted the question. Despite the predictable wrangles caused by the war and the usual disputes about how high to raise prices, OPEC proved that, at 20, it was still very much alive and kicking.

The fact that all 13 members came to the meeting proved that OPEC is more stable and mature than many of its detractors thought.

Another sign of the cartel's elasticity can be seen in the fact that, despite the repeated insistence of the Iranian delegation that the political issues that led to their minister's absence be discussed -- he is held as an Iraqi prisoner of war -- such discussion was ruled out of order in the economic deliberations.

Finally, the agreement on a new, if still loose and multitiered, price increase of an average of 10 percent across the board for the next six months was the conclusive demonstration that OPEC will be around for years.

Even the representative of Iran was conscious of that. Standing in for his boss, who was captured by Iraqi soldiers while on an inspection tour of war-damaged oil facilities, Iran's Deputy Oil Minister Seyyed Hassan Sadat, after brandishing the imprisoned Mohammed Javad Tondguyan's photograph in the opening session and arguing about the subject of Iraq's violations of Iranian rights, was forced to settle down and get on with OPEC business -- proposing and getting a $36-a-barrel ceiling for light crude.

It is a strange sort of solidarity that keeps the organization intact. The war between Iraq and Iran, and the broken diplomatic relations between Libya and Saudi Arabia are the most glaring examples of the deep political disparities.

The organization encompasses the feudal and pro-Western Saudi Arabia; Iraq and Algeria, both nationalistic and socialist; and revolutionary Iran, historically antagonistic to the Arab nations that make up the bulk of OPEC's membership.

The cartel is rounded out by the gulf sheikdoms of Kuwait; Qatar; and the United Arab Emirates -- as feudal as Saudi Arabia, which dominates them -- as well as such different nations as Indonesia, Ecuador, Gabon, Nigeria and Venezuela.

OPEC was brought to life as a reaction by the world's oil producers, who realized that they were being taken to the cleaners by international oil companies -- Gulf, Mobil, Texaco, Exxon, British Petroleum, Royal Dutch Shell and Standard Oil of California. These companies had pioneered the techniques of oil exploration, extraction, refinement and marketing. They reigned supreme, often having more powers in such underdeveloped (at the time) oil producers as Saudi Arabia and Iraq than the countries' own governments.

OPEC as an institution began as a vision by Juan Pablo Perez Alonso, who was Venezuela's minister of mines and development in the 1950s. But the oil companies themselves paved the way. In 1959, in one of those unilateral decisions their boards were so quick to make in those days of imperial power, they decided to cut the price of Middle East oil.

Perez Alonso used the decision to press his case for an oil cartel. A trip to Saudi Arabia ended with a joint communique calling for a common policy to defend the interests of the oil-producing nations.

The companies dismissed such talk and cut prices again in 1960. OPEC was born that fall at a meeting in Baghdad. At the time, the price the companies were paying fr a 42-gallon barrel of oil was below $2.

OPEC began to feel its power in 1969, when Col. Muammar Qaddafi overthrew Libya's King Idris and immediately ordered the 21 oil companies operating in Libya to raise their royalties to the government by 25 cents a barrel or cease operations. After a few months, the companies, led by Occidental Petroleum -- which had few other resources -- caved in, and the balance of power between buyers and exporters changed.

It was not until 1973, however, that OPEC found its true muscle. OPEC's Arab members had long discussed the use of oil as a political weapon to advance their demands for a settlement to the continued occupation of Arab lands by Israel. But it took the war between the then Soviet-supported Arab states and U.S.-backed Israel to make theory reality. The ensuing oil boycott demonstrated once and for all the extent to which OPEC had achieved a stranglehold over the industrial West's oil-thirsty economies.

Following the 1973 war, OPEC discovered it no longer needed to negotiate prices with Western oil companies -- it was enough to dictate. Prices doubled, tripled and quadrupled. The benchmark price of $5.40 a barrel established in 1974 after the embargo had jumped to $14.54 by 1978. It jumped to $30 a barrel in 1979. This year it soared to $41 a barrel for the highest grade crude.

With such economic benefits, it is simple to understand how OPEC survives inherent political strain.

As Kuwait's Sheik Ali Khalifa Sabah put it at the end of this year's meeting: "What we have achieved here is an agreement to limit our disagreements. That is a sign of health and solidarity."