Kiribati president Anote Tong made the call at the Pacific Islands Forum — which started in Port Moresby on Monday — where Pacific nations have gathered to form a united position to take to the Paris COP21 meeting in December.
“What we are talking about is survival, it's not about economic development... it's not politics, it's survival,” Tong said.
Tong said Australia and New Zealand should use their relative regional power to advocate for smaller countries.
“I think they need to come to the party, if they really are our friends then they should be looking after our future as well,” he said.
Kiribati, with its population of 110,000 spread across 33 low-lying islands, is particularly vulnerable to climate change.
Last year, the Kiribati government purchased 20 square kilometres of land in Fiji as a back-up plan for food security and possibly even relocation of its citizens.
The week-long Pacific Islands Forum kicked off with a meeting of a bloc of seven small island states — Cook Islands, Kiribati, Marshall Islands, Nauru, Niue, Palau and Tuvalu.
Prime Minister Tony Abbott will travel to Port Moresby on Wednesday and will take part in the main Pacific Islands Forum leaders retreat on Thursday.
A climate change declaration in Suva last week — at a rival regional forum that does not include Australia and New Zealand — signalled what Pacific countries would likely bring to the negotiating table.
The Suva declaration included a call to limit global temperature increases to 1.5 degrees Celsius, saying the current goal of 2 degrees above the pre-industrial level would push many beyond their ability to adapt.
Oxfam Australia said there has been frustration amongst some Pacific island nations that Australia and New Zealand haven't taken a stronger position on climate change in the past.
“The two big brothers of the Pacific have largely ignored their neighbours' calls for stronger emissions reduction targets and greater support to meet the challenges of climate change,” said Dr Helen Szoke, Oxfam Australia's chief executive.
“The question remains whether Australia will do the right thing by the Pacific and ensure the leaders meeting sends the strongest possible signal ahead of Paris, or whether together with New Zealand, it will use its influence in the Forum to weaken any outcomes,” Dr Szoke said.
The Pacific Island Forum will also discuss alleged human rights abuses in the West Papua and Papua provinces of Indonesia, fisheries, information and communication technology and cervical cancer.