The political and economic crucible into which the Third World's petroleum producers have been forced by the current market surplus is manifest here in Nigeria, black Africa's oil-exporting giant.

With an economy built almost entirely on its rich light crude but with politics shaded by foreign pressures, the government faces the hard choice of lowering prices and risking economic war or cutting production at the expense of domestic well-being.

So far, Nigeria is following the second route, and both the response and the pressures that created it provide an insight into what the oil glut has done to the developing producers of OPEC, the Organization of Petroleum Exporting Countries.

Since January, Nigeria has cut its oil production by more than one-third to maintain the high prices it charged before the surplus -- caused largely by high production by Saudi Arabia. The economic cost has been high: a $3 billion loss of revenue that is threatening to create a domestic economic crunch.

In following a cutback policy, however, Nigeria, which gain 90 percent of its revenue from oil, has not only saved its oil for the time when the world surplus disappears but is honoring a commitment to OPEC's prices policies it fears to break.

There are domestic political pressures to maintain high prices for Nigeria's major exhaustible resource, according to a high-level Nigerian official, foreign analysts and industry sources here. At the same time, the country's petroleum officials must stay in close price coordination with the three other African OPEC members, Algeria, Libya and, to a lesser extent, Gabon, to avoid causing a price-cutting war for their similar, high quality, light crude exports.

At a meeting in Algeria late last month, the four African OPEC producers agreed to maintain prices in the pre-glut range of $40 to $41 a barrel for their oil exports of lowsulfur "sweet" crude, despite oil company pressures to lower prices and sharp production cuts caused by the loss of dozens of customers.

But pricing pressures have mounted. The British, who do not belong to OPEC, in mid-June cut their price for North Sea oil by $4.25, to $35 a barrel, even though in the past the British National Oil Corp. has tied its prices of North Sea oil directly to those of Nigeria, since the two produce similar crudes. At the same time as the British cuts, the spot market price for light crudes dropped to as low as $33 a barrel.

Since the meeting in Algeria, Libya has cut its prices for its top grade of light crude by $1.10, to $39.68. "The Nigerians didn't see that as a price cut," said one Western analyst here, "but rather as the Libyans brining their prices in line to with Nigeria's own $40 a barrel price."

Nevertheless, the Libyan announcement was followed by widespread oil industry and news reports that Nigeria recently agreed to sell $100,000 barrels of oil a day -- starting July 1 -- to unidentified Zurich-based oil traders for a $2.50 discount at $37.50 a barrel.

But Odoliyi Lolomari, acting director of the Nigerian National Petroleum Corp., has publicly denied foreign reports that Nigeria has discounted the price on part of its output, or that it plans to lower prices on all of its production. "We are a responsible member of OPEC," he said, "and, accordingly, we will comply with OPEC's decision taken" at the organization's ministerial meeting in Geneva last May, to freeze prices and cut production between 5 and 10 percent.

Whatever the facts, Lolomari's denials are seen as an effort to head off any domestic charges that the government is bowing to pressure from Western oil customers by reducing prices, a potentially explosive issue in this country's volatile five-party political configuration.

"No one here is going to talk about lowering prices, but if other [OPEC] African producers bolt, Nigeria will be right behind them," said a knowledgeable oil industry source. "Nigeria just won't be the first to lower prices," he added.

In 1977-78, Nigeria went through a severe economic crunch after it raised its oil prices above Algeria's and Libya's and, thereafter, suffered a six-month drop in production of 500,000 barrels a day as its customers went elsewhere. Since that debacle, Nigeria has followed the pricing policies of the two African oil hawks, Algeria and Libya.

With a population estimated at 100 million, the largest in Africa, Nigeria cannot afford to "engage in a price war with Algeria and Libya, so it follows them cautiously," said one Western source.

At the same time, Nigerian President Shehu Shagari's economic adviser, Emmanual C. Edozien, said recently that the country's ambitious $125 billion development plan would be jeopardized if oil exports did not return soon to normal levels.

Development projects would have to be postponed and the country's $23 billion budget cut "if [production cuts] continue through July," said one Nigerian official.

With earnings of $11.2 billion so far this year, a relatively small external debt of $9.8 billion and a foreign exchange reserve of $8 billion, Nigeria is not in any immediate danger. But one informed source said Nigerian officials are counting on the oil surplus drying up relatively soon.