Of all the Eastern European and Third World countries reeling from the impact of higher oil prices and the international trade embargo that followed the Iraqi invasion of Kuwait, few stand to lose more than Poland.

According to Polish diplomats, their country's fragile economy stands to lose $1 billion in arms sales and construction contracts because of the worldwide embargo on trade with Iraq, which had been Warsaw's main partner in the Middle East, plus uncounted millions of dollars it will have to pay out because of higher oil prices.

The economic impact on the Polish economy is just one example of the rippling effects on Third World and Eastern European nations of the embargo on trade with Iraq and Kuwait and the increase in oil prices that followed from taking about 4.5 million barrels a day of oil off of world markets.

Analysts said continued high oil prices could impede the transformation of the formerly communist nations of Eastern Europe to market-oriented economies, set off another redistribution of the world's wealth that would leave poorer nations even further behind, and make it harder for South American nations such as Argentina and Brazil to shake off their heavy debt burden.

But poorer countries with oil reserves stand to enjoy a windfall. The Soviet Union, a major oil exporter desperate to restructure its economy, expects to gain $1 billion a year for every $1 a barrel increase in the price of oil.

Oil prices have gone up about $9 a barrel since Iraq precipitated a Mideast crisis that culminated in its invasion of Kuwait 10 days ago.

Third World oil exporters such as China, Mexico and Indonesia also stand to gain economically from the current crisis.

But a senior Mexican official here last week discounted the short-term windfall and predicted problems for his country if the U.S. economy falters as a result of higher oil prices.

He said a strong U.S. economy is more important for long-term Mexican prosperity than an increase in the price of oil.

On balance, trade experts said the negative impact of higher oil prices and a trade embargo with Iraq and Kuwait greatly outweigh any gains.

Poland, for example, has been involved for the past 20 years in major highway and other construction projects in Iraq that employed 4,000 workers who will no longer be paid in hard currency, Polish diplomats here said.

Further, the officials feared that Poland would lose the construction equipment it had paid for and brought to Iraq for the projects.

In addition, most of Poland's exports of armaments, especially tanks, went to the Iraqi military. These sales have been stopped by the embargo.

The diplomats said Iraq presently owes Poland $500 million for the shipment of goods and another $500 million for construction contracts.

Much of the payment came in the form of oil shipments from Iraq, saving Poland the need of using its scarce hard currency resources to buy the oil.

A Polish diplomat said a large shipment of Iraqi oil, a partial payment on its accounts, was due to be loaded on a tanker in Turkey this week but was stopped by the embargo.

The diplomats said the rising price of oil, the difficulty of gaining new oil supplies and the loss of sales to Iraq will hurt a Polish economy that already is reeling from eight months of shock treatment as it tries an instant conversion of its state-controlled communist system to one driven by market forces.

Christopher Potts, an economic analyst with Banque IndoSuez in Paris, told Knight-Ridder Financial News that Eastern European countries such as Poland stand to be major losers from the embargo and oil price rise.

"They no longer have the assurance of the Soviet energy umbrella, and now they are going to find price increases fed through to them very quickly," he said.

Eastern Europe used to be largely insulated from the ups and downs of world oil prices, with most of its supplies coming from the Soviet Union on barter arrangements priced in rubles.

This system is being dismantled, however, and as contracts expire, they are to be renegotiated on world market, hard-currency terms.

In general, this will mean better times for the Soviets because it will inflate the value of what is already their most important export.

"Over 70 percent of their hard currency is coming from oil and gas exports to the West," noted Daniel Yergin, president of Cambridge Energy Research Associates.

Hoping to satisfy its citizens' demands for a higher standard of living, the Soviet Union is anxious for hard currency to finance imports.

With the new rules of the oil trade, "they are generating something worthwhile," said Bernard Picchi, managing director at the Wall Street securities firm Salomon Brothers Inc., "whereas before they were simply giving their oil away in return for shoddily made goods."

Romania, the only oil exporter in Eastern Europe, also has reason to be happy. Noted Peter Beutel, a vice president at Merrill Lynch Futures: "They actually have been one of the biggest suppliers of gasoline to the United States over the years."

But Brazil, a net importer of oil, is a potential loser, economists said. It is scheduled to begin talks with banks soon over a restructuring of its $115 billion foreign debt.

"A major oil price increase would leave them with nothing left for paying the banks," said Rudi Dornbusch, professor of economics at the Massachusetts Institute of Technology.

Other South American countries with major debt and no oil income, such as Chile, also would find costly oil a disturbing reality.

The countries of sub-Saharan Africa, perhaps the poorest region of the world, would also take a serious hit, facing soaring import bills at a time when they are still struggling just to subsist.

The high-growth economies of East Asia outside of Japan, all almost totally dependent on oil imports, are expected to find their forward momentum slowed by higher oil prices.

The Philippines, the prime debtor of the region, would find its problems mounting. The Philippines already suffers from a mounting trade deficit, about $1.59 billion in May, which will worsen as oil prices increase. Similarly, higher oil prices will likely add fuel to Manila's 13 percent inflation rate, analysts said.

They also could cause further problems for South Korea's deteriorating trade picture and cause losses of billions of dollars in construction income from projects in both Iraq and Kuwait.

South Korean firms have 13 construction projects under way in Iraq and four in Kuwait, worth a total of $2.5 billion.