Chief Cabinet Secretary Takeo Kawamura expressed disappointment Monday after Iran convicted an American journalist of Japanese descent of spying for the United States.

"It is regrettable," Kawamura told a press conference, referring to news Saturday that Iran sentenced Roxana Saberi, 31, to eight years in prison. U.S. President Barack Obama has also expressed deep disappointment.

“We would like to wait and see what the United States and Iran will do,” he said, adding that Japan, as a country with friendly ties with Iran, could “serve as a mediator” between Washington and Tehran in case dialogue between the two break down over the matter.

Saberi, a dual American-Iranian citizen born to an Iranian father and a Japanese mother, was arrested in late January.