The Justice Ministry cannot grant citizenship to a Japanese couple's twins born to a U.S. surrogate mother under the existing legal framework, but is making efforts to resolve the issue as swiftly as possible, Justice Minister Daizo Nozawa said Friday.

The twin boys were born in California last fall and have been living with the Japanese couple in the Kansai region since spring as U.S. citizens.

The ministry has yet to accept the notification of the boys' births, saying it cannot confirm the parent-child relationship. This confirmation is necessary when the mother in the documentation is aged 50 years or older. The Japanese woman is 55.

During a news conference after Friday's Cabinet meeting, Nozawa said the issue requires debate on the national level regarding the country's policy on surrogate births and the status of children born through such procedures.

"We must wait for a consensus on how society views parents who want children," Nozawa said. "But discussions to gain such a consensus have not fully taken place, even within the circles of medical science (in Japan)."

Nozawa said it is the first time "such a complex case" involving an overseas surrogate birth was confirmed.

The ministry acknowledged, on the other hand, that the couple's case has been up in the air for too long and ministry officials said they hope to pass final judgment on the matter as soon as possible.

The Japan Society of Obstetrics and Gynecology bans surrogate births. In its report on planned legislation on fertility treatment, a Health, Labor and Welfare Ministry panel recommended in April that domestic surrogate births be banned, but it fails to address cases in which Japanese couples pursue surrogate births overseas.