Cuban Foreign Trade Minister Marcelo Fernandez Font said yesterday that Cuba has financial claims against the United States greater than the $1.8 billion in American-owned property confiscated by Fidel Castro's Communist regime.

At a conference here on promoting greater U.S. Cuban trade. Fernandez parried questions about the claims issue by saying: "We think we shoud receive compensation for damages done to our economy through U.S. actions."

These damages, he asserted, resulted from the U.S. trade embargo against Cuba in effect since 1962 and from "former aggressions" such as the U.S. - support, abortive 1961 Bay of Pigs invasion by anti-Castro Cuban exiles.

Although the Castro government has not yet calculated the cost of these damages. Fernadez said, "It is very high - higher than the amounts claimed by the United States."

In addition, Fernandez added, a restoration of normal trade relations would require the United States to life the embargo, grant Cuba "most favored nation" tariff status and provide access to American financing.

But, despite his stress on these problems. Fernandez took a generally upbeat tone in discussing the possibilities of U.S. Cuban trade. If normal trade is restored, he said. U.S. exports to Cuba could total $350 million in the first year and rise to more than $1 billion in three or four years.

In fact, Fernandez - the first cabinet-level Cuban official to visit Washington since 1962 - was here yesterday because of increasing expectations that Cuba might again become a big market for U.S. exports. His unofficial visit was to take part in the conference sponsored by the East-West Trade Council, a private organization seeking broadened trade with Communist bloc countries.

The talk about trade comes against background of movement by Washington and Havana toward improved ties. To provide better diplomatic communication, the two governments opened "interest sections" in each other's capitals last month; and diplomatic circles expect that the formal relations broken off in 1961 will be resumed within the next few months.

First, though, a number of problems must be resolved on both sides. State Department officials have stressed repeatedly that, from the U.S. point of view, the most difficult obstacle involves settlement of the claims for U.S. property and assets seized by the Castro regime after it came to power in 1959.

The Foreign Claims Settlement Commission, an independent federal agency, calcutes the total allowable value of these claims at $1.8 billion - $1.6 billion of that amount in assets lost by U.S. business firms and $200 million in small claims by individual U.S. citizens.

In response to questions about these claims. Fernandez said the Castro government would discuss them only if the United States is willing to negotiate Cuba's counterclaims for damages.

The Cuban claims, he asserted, do not include damages for loss of life in the Bay of Pigs invasion and a "long series of other aggressions through the years" by Cuban exiles operating from the United States.

Instead, Fernandez said, he was referring only to property damaged by "aggressions" and "commercial losses" caused by the embargo and its severing of the formerly close trade dependency that Cuba had developed on the United States.

The embargo, he said, had deprived Cuba of its share of the old U.S. sugar quota, had cut the island country off from its principal fuel supply and had forced Cuban factories and other enterprises "into years of idleness of reduced capacity" because of their inability to obtain American-made spare parts.

In talking about future trade possibilities. Fernandez said Cuba was interested in buying from the United States foodstuffs, animal feeds, drugs, fertilizers, ferrous and nonferrous metals and machinery and other industrial equipment including entire plants.

In exchange, he added, Cuba would like to re-establish the United States as a market for its principal commodity, sugar. It also wants to sell tobacco, shellfish and nickel, he said.

Fernandez warned that it would not be sufficient for Washington to ease the embargo by allowing the sale of American foodstuffs and drugs to Cuba, while continuing to prohibit the impart of Cuban products.