The mayor of Setagaya Ward, Tokyo, said Thursday he will consider publicly acknowledging long-term, same-sex couples as family members, following a groundbreaking proposal by another ward in the capital to do so by issuing certificates.

"I hope to realize what is possible within my authority as ward mayor," Nobuto Hosaka told reporters.

"It's important to respect diversity in our society going forward," the mayor said, expressing hope to start official recognition of same-sex couples "as soon as possible."

Earlier this week, Shibuya Ward submitted an ordinance to its assembly that would recognize same-sex couples as being in "relationships equivalent to marriage." Passage of the ordinance would mark a first in Japan.

Although legally nonbinding, such a move could eventually influence the central government. The Constitution defines marriage as "based only on the mutual consent of both sexes."

Hosaka made the remarks after receiving a request from a Setagaya Ward assembly member who has gender identity issues, saying the ward should issue certificates to recognize gay couples.

However, the mayor expressed reservations about crafting an ordinance as Shibuya Ward did. "I don't think it's absolutely necessary," he said.

Gay couples in Japan often face discrimination when moving into apartments together or visiting partners in hospital, on the grounds that they are not relatives.