SYDNEY, AUSTRALIA - Spain's King Juan Carlos and Queen Sofia concluded their first official visit to Australia in more than two decades Friday with an address to business leaders in Sydney.

The three-day trip is said to be part of an effort to lift Spain's profile in the Asia-Pacific region.

The king told delegates at the Spain Business Forum that his nation shared "valuable and outstanding" similarities with Australia, including an increasingly knowledge-based economy and highly liberalised foreign trade.

Spain's relationship with Australia was particularly well developed in the defence industry field and Spanish companies would take part in the building of desalination plants here, the King said, according to the AAP newswire.

As the final engagement of their visit, the royals attended a luncheon reception hosted by Marie Bashir, the governor of New South Wales.

The royals' last official visit to Australia was during the Brisbane Expo in 1988. They also attended the 2000 Sydney Olympics in what was classed as a private trip.