Taiwan’s panel of grand justices will announce its verdict on whether Taiwan’s current marriage law is unconstitutional on Wednesday, which could make the country the first in Asia to legalise same-sex marriage.

LGBT and human rights activists are cautiously optimistic on the ruling. The bid for same-sex marriage has gathered steam over since the Democratic Progressive Party took office last year and parliament are currently debating a same-sex marriage bill.

"I feel 100 percent confident about a positive outcome," Chi Chia-wei told Agency-France Presse, 59, one of two parties petitioning the constitutional court.

"I am optimistic but I wouldn't be overly excited. This should have happened long ago," said the activist who made his first submission for recognition of gay marriage in 1986.

The other plaintiff is Taipei city government which is seeking clarification on the issue after denying marriage licences for gay couples.

Observers have outlined three possible outcomes. The judges will either take no action, advise the government amend the civil code on marriage to include same-sex partnerships, or suggest a new partnership law be enacted specifically for same sex couples.

"Everyone is really looking forward to the decision, not only in Taiwan but across Asia," said Lu, an activist with rights group Taiwan LGBT Hotline Association, citing campaigns in Japan and South Korea.