The work-style reform promoted by Prime Minister Shinzo Abe is an important step in reining in excessive overtime, but the real challenge is to sustain long-term momentum, the chief of the International Labor Organization said.

Guy Ryder, director-general of the ILO, lauded the government's push to address the issue but warned that effort is required to ensure it remains more than just a flash in the pan.

"I welcome the fact that some first steps have been taken to address this long-standing Japanese phenomenon, excessive working time," Ryder said Saturday in an interview. "The real challenge would be to maintain the momentum."