While business sentiment among Japan's large manufacturers in the July-September quarter was the highest in more than 13 years, the future looks far from rosy.

The widely watched "tankan" quarterly survey released Friday by the Bank of Japan shows that manufacturers are uncertain about the next three months due to surging crude oil prices -- indicating the country's economic recovery might be finally running out of steam, economists said.

The quarterly survey showed that the business confidence index for large manufacturers improved to 26 from 22 in June, the sixth consecutive quarterly rise. The index represents the percentage of companies reporting conditions are good minus those reporting otherwise.