Australia's Art Gallery of New South Wales has revealed it plans to double in size and transform itself into an art museum for the "Asian century", in time for the 150th anniversary of its founding in 2021.

An international architectural competition will produce a design for the new building, which will expand northwards towards the harbour.

Other improvements - part of a strategic master plan for the attraction - include new acquisitions, technology to engage audiences around the world, initiatives to cater to non-English speakers, better transport connections and dining facilities.

To top it off a spectacular grand entrance with commissioned artworks will link the existing heritage building with the new building.

President of the gallery board Steven Lowry said: "We have the opportunity to create an iconic building that will take its place alongside the Sydney Opera House and the Harbour Bridge as an international beacon of modernity, creativity and the celebration of the human spirit."

Lowry said Sydney risked being left behind by projects now underway in Singapore, Hong Kong and San Francisco.

The gallery will now consult with stakeholders, including the NSW government, the Royal Botanic Gardens, transport authorities, the artist community and friends and supporters of the art gallery.