President Carter's diplomatic pressures on Nicaraguan President Anastasio Somoza were applauded yesterday by five senators who urged that Carter "seriously consider further political and economic actions" if Somoza does not cooperate in efforts to bring democracy to his Central American country.

This course was recommended in a letter sent to Carter by Sens. Edward M. Kennedy (D.-Mass.), Alan Cranston (D.-Calif.), Mark O. Hatfield (R.-Ore.), Jacob K. Javits (R.-N.Y.) and Paul S. Sarbanes (D.-Md.).

On Thursday, Carter ordered drastie reductions in US. aid to Nicaragua and in U.S. official personnel there because of Somoza's refusal to accept a U.S.-sponsored mediation plan for an internationally supervised plebiscite on his rule.

The mediation effort was made after Nicaragua erupted last September into civil war between Somoza's National Guard troops and civilians led by leftist guerrillas.

In their letter, the senators said, "We welcome and support your recent actions to dissociate the United States from the Somoza government." Calling attention to reports of widespread human rights violations in Nicaragua, they also said that if Somoza continues his dictatorial rule further steps should be taken.

Such steps, the senators suggested, could include: collective pressures in cooperation with other American states, withdrawing the U.S. ambassador, opposing loans to Nicaragua by international lending institutions, cutting off imports of Nicaraguan sugar and meat and refusing Nicaragua credits from the Commodity Credit Corp., and Export-Import Bank.