Australia–New Zealand relations, also referred to as Trans-Tasman relations due to the countries being on opposite sides of the Tasman Sea, are extremely close with both sharing British colonial heritage and being part of the Anglosphere. New Zealand sent representatives to the constitutional conventions which led to the uniting of the six Australian colonies but opted not to join; still, in the Boer War and in World War I and World War II, soldiers from New Zealand fought alongside Australians. In recent years the Closer Economic Relations free trade agreement and its predecessors have inspired everconverging economic integration. The culture of Australia does differ from the culture of New Zealand and there are sometimes differences of opinion which some have declared as symptomatic of sibling rivalry. This often centres upon sports such as rugby union or cricket or in commercial tensions such as those arising from the failure of Ansett Australia or those engendered by the formerly long-standing Australian ban on New Zealand apple imports.