The head of Japanese whisky maker Suntory says merging Japanese and American work cultures remains a major challenge in his company's acquisition of the maker of Jim Beam bourbon.

Takeshi Niinami, the president of Suntory Holdings Ltd., said Friday that integration is not easy because of differing career aspirations and compensation systems for Japanese and American employees.

Suntory bought the former Beam Inc. in 2014.

Niinami said his goal is to create a global workforce that shares ideas freely. He conceded, though, that he doesn't have a solution yet to overcome the differences.

He said the combined Beam Suntory will have to concentrate on integration for at least three to four years, so it has no interest in additional acquisitions for now.