The Organization of Petroleum Exporting Countries reduced its official prices today for the second time this year. But the cuts appeared to be too small to do much to halt the long-term slide in world oil prices, petroleum industry analysts said.

They added that the failure of Saudi Arabia to persuade its fellow OPEC members to take effective action to regain control of the world market testified again to the eroding political influence of the world's richest oil producer.

The token drop of 50 cents a barrel for heavy crude and 20 cents a barrel for medium grade oil fell far short of Saudi Arabia's original demand for a $1.50 cut that would have brought the cartel's prices more in line with the free market.

Only 10 of the 13 cartel members consented to the new price agreement. Iran, Algeria and Libya refused to give their blessing to any reduction in prices.

The caution displayed in foreign affairs by the conservative desert kingdom under King Fahd also has characterized its oil policy in recent years. While aware of its strategic importance, Saudi Arabia has shown reluctance to use the full power of its wealth and vast oil reserves to promote its interests.

As prices have slipped amid a burgeoning oil glut, the Saudis have tried to gain support for their views by threatening to flood the market with oil and drive down prices as low as $10 a barrel unless other producers, both in and out of OPEC, showed a willingness to cooperate in managing the market.

Yet repeatedly, Riyadh has backed away from such threats as slackening demand has forced its output to dwindle from nearly 10 million barrels a day in 1979 to barely 2 million barrels today. National income has fallen so sharply that financial reserves are being drawn down by $1 billion a month to pay for existing government programs.

OPEC delegates said that while the Saudis might be able to survive better than most in a world of $10-a-barrel oil, the political upheavals that would ensue would pose a much graver threat to the stability of the Persian Gulf sheikdoms.

"Going to 9 or 10 million barrels a day by the Saudis is like going nuclear in a war," one OPEC analyst said. "It could wipe out everybody."

Perhaps because this scenario has taken root, Saudi demands for rigid adherence by the 13 members to OPEC's fixed prices and production quotas have gone largely unheeded.

Many countries have persisted in offering secret discounts or pumping more than their share of oil in desperate attempts to maximize their revenues during the protracted slump. As a result, Saudi Arabia has been losing customers because it generally insists on sticking to official prices.

At the six OPEC meetings held in the past year, Saudi Arabia has warned repeatedly that it would not tolerate a continued decline in its output just to underwrite, in effect, the "cheating" of the other members and the unrestrained oil production of countries outside the cartel such as Britain, Norway, Mexico and the Soviet Union.

Indeed, the rapid expansion of output by the non-OPEC producers has whittled the cartel's share of the world market from two-thirds to one-third in the past five years.

Within OPEC, the Saudi reputation for bluffing has become so entrenched that Oil Minister Ahmed Zaki Yamani, who repeatedly has delivered the dire but unfulfilled threats about his country's intentions to enforce its will on the market, has lost much of his credibility with his peers.