Mr Abbott congratulated Mr Key for New Zealand's commitment to 143 Defence Force personnel to work alongside Australia in Camp Taji to train Iraqi troops for two years.
He said the fight against Isis was an international fight and it was a "right and proper" decision by New Zealand."
"As far as I am concerned, good on John Key for being there to shoulder a reasonable share of responsibility for this particular battle because the death cult is reaching out to the world.
"Australia is proud ot be part of an internaitonal coalition working to disrupt and degrade and ultimately to destroy this death cult.
"It is the world's fight and it is important that New Zealand and Australia be involved.
It is the latest example in a long, strong and intimate partnership."
Commenting on Mr Abbott's leadership, Mr Key said he was an outstanding Prime Minister and it was a privilege to work alongside him, however the question of the Liberal leadership was a matter for the party.
Mr Abbott joked that the pair had discussed the issue of leadership: "and I can say that John's leadership is safe."
He said the latest speculation about the leadership of the Liberals was "media hyperventilation."
The pair are lunching together and will watch the one-day cricket match at Eden Park between Australia and New Zealand.