The Prime Minister will head for the United Nations in New York on Sunday, where about 160 other leaders will gather for the General Assembly.
John Key said it would be a busier meeting than normal, as it would include the adoption of sustainable development goals and mark the 70th anniversary of the UN.
Mr Key will also attend President Barack Obama's leaders' summit on countering Islamic State and violent extremism.
The Prime Minister will hold formal and informal meetings at the UN, as well as with the New York business community.