Washington — Somalia's President Siad Barre has come to Washington sounding an alarm about Soviet expansionism and calling for more aid to his nation located on the strategic Horn of Africa.
In an interview with the Monitor, President Barre said the West had been slow to respond to Soviet moves in Africa and on the oil-rich Arabian Peninsula. But he praised President Reagan for the firm statements he has made regarding the Soviets. President Barre met with Mr. Reagan at the White House on March 11.
Although Barre was not specific about it in the interview, other sources indicated that the Somali leader is asking Reagan for:
* A speed-up in delivery of military equipment the US has promised to Somalia.
* A considerable increase in both the amounts and types of new equipment.
* More economic assistance, including long-term loans, credits, and loan guarantees as well as more than $200 million in financing for a dam and irrigation project.
In explaining what Barre means by new types of military equipment, one source said ground-to-air, antiaircraft missiles. As the Somalis see it, the antiaircraft guns the US had earlier promised to Somalia are not capable of countering the Soviet-built MIG fighters which they say make almost daily raids from Ethiopia into Somalia.
Barre was diplomatic when it came to commenting on the $42 million in ''defensive'' military equipment that was promised to Somalia under a 1980 agreement with the US. He suggested delays in delivery of this equipment may have been due to the slowness of the American bureaucracy.
''We have to be satisfied with the American system,'' the Somali leader said. ''. . . One cannot overlook a friendly country's system. But if it was me, I would have been more speedy to cope . . . with a potential threat coming from opposing forces.''
Barre added that in his meeting here on March 10 with Secretary of Defense Caspar Weinberger, Weinberger said he would try to expedite the delivery of already promised military equipment to Somalia.
Other Somali officials said Somalia had yet to receive any of that equipment. A source close to Barre said that when Somalia had no US equipment to display at a national day parade last October, leftist opponents of the government claimed American support for Somalia had come to nothing.
''It seems that the Soviets are exploiting the slowness of the West,'' said Barre, who also asserted that Soviet-backed Libya was financing Ethiopian actions against Somalia.
The Somali President asserted as well that the Soviet Union had gained influence in 17 Africa countries by playing on popular dissatisfactions in the region and by being quick to move new weapons in.
Somalia, once allied with the Soviet Union, expelled all Soviet advisers and technicians in 1978, giving them only seven days to leave.Barre claimed the Soviets (1) wanted to impose their system on Somalia, (2) wanted to use Somalia as a ''stooge'' regime as a part of their larger designs on the region, and (3) aligned themselves with the Ethiopians, whom he described as the ''centuries-long enemies of Somalia.''
Barre said Libya, with the support of the Soviet Union, had nearly destroyed the nation of Chad and threatened other regimes in the region. He said Libyan leader Col. Muammar Qaddafi ''is a nice person when you are with him. But when he walks out the door, you don't know what he will do next.''
Somalia is one of the world's poorest nations, depending heavily on the export of livestock and bananas. But Barre says his country offers great potential for American companies in the fields of oil, industry, and water resources. Texaco is currently exploring for oil in Somalia.