The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Mr Wright started a relationship with Elizabeth after divorcing three earlier wives.

Olivia is the youngest of Mr Wright's four children but she had a difficult relationship with her father, who was frequently absent and gave little support for her single mother before his death in 2012.

She had not met older siblings Leonie Baldock, Alexandra Burt and Myles Wright prior to his death.

Olivia challenged her father's will because her $3 million trust fund had onerous conditions and could not be accessed until she was the age of 30.

Related Articles

She sought an immediate $12 million share of her father's estate, estimated at more than $1 billion, but in February the WA Supreme Court instead awarded her $25 million, the largest such payout in Australian legal history.

Olivia told the Seven Network's Sunday Night program there had been many personal hurdles during her long legal battle.

While she is ready to contest the appeal, she said she's unsure if she would go through the initial legal battle again.