In 1951 the United Kingdom became increasingly focused on its European interests, while New Zealand joined Australia and the United States in the ANZUS security treaty. The influence of the United States on New Zealand weakened following protests over the Vietnam War, the refusal of the United States to admonish France after the sinking of the ''Rainbow Warrior'', disagreements over environmental and agricultural trade issues, and New Zealand's nuclear-free policy. Despite the United States's suspension of ANZUS obligations, the treaty remained in effect between New Zealand and Australia, whose foreign policy has followed a similar historical trend. Close political contact is maintained between the two countries, with free trade agreements and travel arrangements that allow citizens to visit, live and work in both countries without restrictions.  there were about 650,000 New Zealand citizens living in Australia, which is equivalent to 15% of the population of New Zealand.