It was a case of botched congressional diplomacy on the part of Secretary of State Alexander Haig at a White House dinner not long ago. The occassion was the May state dinner to honor Japan's prime minister, and among the guests was Sen. Spark Matsunaga (D-Hawaii). But during cocktails before dinner something odd began happening to Matsunaga.

"My wife and I kept wondering why in the world, when I'd talk to Sen. Jackson on someone, an aide would escort us back to the Japanese," says Matsunaga.

Then, before president Reagan's arrival and the start of the dinner, the Japanese and American guests were placed in separate waiting rooms. Matsunaga, a native-born American of Japanese ancestry, was herded into the waiting room with the Japanese. The only other American there: Alexander Haig.

The American secretary of state made his way through the assembled Japanese, introducing himself to Prime Minister Zenko Suzuki's retinue of aides and advisers. Then he approached Matsunaga to welcome him to the United States. A bemused Matsunaga put on his best dime-store Japanese accent and told Haig that it had been his pleasure to vote for his confirmation in the Senate.

you should have seen his face," said Matsunaga.

An obviously flustered Haig still did not recognize Matsunaga. It took a helpful Japanese visitor to identify the senator for the secretary of state.