The government of Guyana expressed "surprise" and "puzzlement" yesterday at the U.S. veto of a $20 million low-interest loan to Guyana from the Inter-American Development Bank.

The IADB is being "used as an instrument for promoting the economic doctrines of the U.S. government," charge d'affaires Colin Mapp contended. The veto will "unnecessarily polarize" U.S. relations with other Latin American and Caribbean nations by making the IADB "degenerate in effect into a one-man show," he said.

Guyanese rice producers would have been the main beneficiaries of the loan. U.S. officials objected because they thought the loan was not based on "sound economics."

The left-wing Guyanese government's pricing regulations, which effectively subsidize the cost of rice to consumers, is a disincentive for farmers, U.S. officials said. They denied that the veto had political overtones.

"What might be proper economics in the United States is not automatically proper economics in Guyana," the Guyanese official said. The United States apparently failed to see Guyana's economy and culture "in a total sense," he said.

Guyana, whose faltering economy depends heavily on sugar and rice exports, will reapply to the IADB for an ordinary capital loan at higher interest rates, he said.