Secretary of Agriculture John R. Block yesterday poked fun at the "logic" employed by his opponents in an internal administration debate over the sale of surplus American butter.

Block appeared to be referring to Secretary of State Alexander M. Haig Jr., who has lobbied hard to prevent a sale of surplus butter to the Russians.

Speaking to dairy interests meeting here yesterday, Block was asked why the United States was trying to sell surplus butter to New Zealand at a lower price than could obtained in a sale to the Soviet Union. "There are some in this administration," Block replied in an oblique reference to Haig, "who would prefer that we not sell to the Soviet Union. Frankly, I just would prefer to sell."

Then Block was asked if U.S. butter sold to New Zealand would end up in the Soviet Union.

"It won't, probably," Block replied, "but some of their [New Zealand's] butter will." At this the delegates to the National Milk Producers Federation meeting burst out laughing. "Don't talk to me about the logic of it because I didn't formulate the logic," Block said, joining the laughter.

By selling to New Zealand instead of more directly to the Soviet Union, the U.S. would lose $15 million approximately" on a sale of 200 million pounds of butter, Block said.