Why US Embassy in Portugal appears to favor Socialists

The United States Embassy in Lisbon has the reputation among Western diplomats here of hoping former Prime Minister Mario Soares and his Socialist Party will return to power.

With the governing right-wing coalition in complete disarray, this wish looks as if it may come true in Portugal's elections April 25.

''It is no use speaking to the American diplomats here. They are so blinkered about Mario [Soares] that they cannot conceive of any other solution to Portugal's problems,'' said an official at another Western embassy.

What lies behind this enthusiasm is a combination of history, US interests in Africa, and a desire to see this small but strategically important NATO country finally achieve political stability.

In 1975, however, Soares and the Socialist Party drove the military leaders - who had seized power a year earlier - and their communist allies from government. It was then that Soares forged a friendship with the new US ambassador to Lisbon, Frank Carlucci.

The memory of this link between Soares and the US Embassy cast a shadow over relations between Lisbon and Washington when right-wing leader Francisco Sa Carneiro became prime minister in January 1980. Mr. Carlucci had always studiously ignored Mr. Sa Carneiro and the US Embassy had made the mistake of predicting the Socialists would win the December 1979 elections.

In many ways, political observers say, history has vindicated the embassy's political judgment. After three years of right-wing rule, Portugal's economy is in turmoil. The feeling is that the Socialists would be able to get labor unions to agree to financial belt-tightening, as they had done in 1978 when Soares secured a standby loan from the International Monetary Fund and committed Portugal to a program of economic austerity.

Democracy is still young and fragile here, and Portugal is among the poorest countries in Western Europe. The US appears to think that in these circumstances , Socialists are the best safeguard against communist influence.

Political observers say this seems all the more true because Soares is one of the most right-wing socialist leaders in Europe. There are, however, still enough radicals in the party to give it a mildly left-wing flavor.

No US embassy likes to be identified as partisan, but US interests appear to coincide with what Socialist leaders want.

One priority in Washington's relations with Lisbon is Portugal's reconciliation with its former African colonies, particularly Angola and Mozambique, the potentially richest ones and those closest to South Africa.

The Socialist Party is confident it can bring the Marxist regimes in these two countries back into the Western fold. Party leaders describe the US as enthusiastic about this.

The Socialists say Mozambique and Angola long to reach an accommodation with the West, but are anxious not to lose face. The Socialists apparently think they could help by offering a stamp of left-wing respectability.