"I don't know yet," the 29-year-old told AFP through an interpreter when asked if he would face his 16 rivals, including record-holder Joey Chestnut, at the annual July 4 hot dog-eating event sponsored by Nathan's Famous, a weenie-emporium in New York's Coney Island.
International Federation of Competitive Eating chairman George Shea said Kobayashi would compete "under huge burden. He has arthritis in the jaw," after his dental surgery.
"I am going to rest today," said the Japanese champion, who denied his jaw problem was a ploy to disconcert his rivals. "I don't have time for this," he said.
The 70-kilo (154-pound) Kobayashi has caused a sensation by winning the contest six year in a row; last year by eating an astounding 53-3/4 hot dogs with buns and all in the stipulated time of 12 minutes.
Chestnut, at 97 kilos (215 pounds) and 23 years of age came second with 52 hot dogs, but this year feels confident after breaking the world record in June with 59-1/2 hot dogs.
"I am looking to eat 60 hot dogs or 61, and break my own record," he told reporters.
Nathan's Famous Hot Dog Eating Competition has been held every year at Coney Island since 1916 and is considered the blue ribbon event of the increasingly popular and lucrative competitive eating calendar.
Most participants now use the "Solomon technique" patented by Kobayashi, breaking the wieners in half before wolfing them down. The buns are eaten separately after being dunked in water to make them easier to swallow.
The only real rule is to avoid regurgitation -- or "reversal of fortune" as it is quaintly termed -- which would result in immediate disqualification.