If New Zealand did not have the resources to fly someone out of a country or have the resources to help a citizen in another part of the world, others would.
"Even if the contribution is small - of course it will be proportional - there has to be some contribution," he said.
"It is the price of the club."
The Five Eyes intelligence alliance began in 1946 between the US and Britain.
!n 1985 changes were made to the longstanding Anzus alliance with Australia and the US due to New Zealand's anti-nuclear stance. But New Zealand signed the Wellington Declaration with the United States in 2010 and the Washington Declaration in 2012 to symbolise closer diplomatic and defence relationships.
Mr Key indicated yesterday that a decision would be made about mid-February after Cabinet had considered the options.
He visited London en route to Bosnia and Herzegovina to chair an executive meeting of the International Democrat Union of centre right parties.
He will then attend the annual World Economic Forum in Davos, Switzerland, with Trade Minister Tim Groser.
Watch: New Zealand PM: 'We must help fight against Islamic State'