Iran added a surcharge of 60 cents a barrel onto the price of its crude oil today raising the prospect of a new round of unilateral price increase by other members of the Organization of Petroleum Exporting Countries.

The surcharge comes on top of a two-tiered one imposed less than a month ago and raises the price of Iranian oil to $17.17 a barrel for light crude and $16.64 for heavy.

Amounting to a 3.8 percent price rise, the surcharge is to take effect Tuesday, the National Iranian Oil Company said. It will, however, be retroactive, affecting all contracts signed since April 1, a company spokesman said.

Ian earlier imposed surcharges of $1.90 and .80 per barrel, respectively, for light and heavy crudes, effective April 15, in line with other OPEC surcharges.

The new unilateral surcharge came as a surprise to Western oil industry representatives, who consider such a non-OPEC increase affecting signed deals as unusual, if not unethical.

However, it appeared that Iran's oil customers, in view of the tight world market, have little choice but to accept the increase and pass it on to consumers, industry sources said.

The oil company spokesman said market conditions justified the price rise but they declined to elaborate.

Since Iran resumed exporting oil following a series of paralyzing strikes leading up to the February revolution, the National Oil Company has signed nine-month contracts with at least 36 foreign oil companies and governments, accounting for export commitments of about 2.3 million barrels a day.

In accordance with a government ceiling on output, Iran currently produces about 4 million barrels of oil a day compared to a prerevolutionary average of about 5.8 million a day. About 3.5 million barrels a day are available for export. This is 1.6 million barrels a day less than before, contributing significantly to he current tight world market.

In addition to the 2.3 million barrels a day already committed, the oil company has potential customers for 700,000 barrels a day, industry sources said. As many as 300,000 barrels a day are kept for sale on the spot market, and about 200,000 barrels a day of refined products are available.

Including the latest surcharges and assuming exports at the available levels. Iran can expect to earn about $21 billion in oil revenue this year, matching the income figures from previous years when Iran exported more.

That essentially means that Iran's main economic problem will not be a shortage of funds, as was feared during the revolutionary strife, but how to spend the oil billions effectively.

This is not as easy as it wounds, economists say, because the new government lacks the skills needed to administer such sums. Perhaps more important, a variety of political problems-including the question of ownership and workers' participation in industrial management-remain to be solved before the oil money can be pumped into the economy again.

Political uncertainty also could hinder Iran's ability to maintain its oil income. One of them is the possibility of renewed disturbances resulting from growing polarization between rightist Islamic supporters of Ayatollah Ruhollah Khomeini, Iran's de facto head of state, on the one hand and liberals and leftists on the other.

Moreover, labor problems in the southwestern oil-producing region add another element to the potential for disruption.

A recent dispute between National Oil Company management and labor in the oil-refining center of Abadan threatened to precipitate a strike, industry sources said. Workers' committees demanded the dismissals of six managers, and the company head, Hassan Nazih, acceded, they said. Then all the managers in Abadan resigned in solidarity with the six, and Nazih was forced to reinstate them.

"Both the workers and the managers were angry, and Nazih lost face with everybody," a source said. Subsequently there have been reports of mounting calls for Nazih's replacement.