Thirty New Zealand defence force personnel are on the American warship, the USS Cleveland, which is anchored off Luganville on the Vanuatu island of Santo.
They are there as part of a mingling of New Zealand and US forces in the multi-nation, American-led aid mission, Pacific Partnership.
The troops will be under US command while onboard the Cleveland.
Meanwhile, the New Zealand ship, the Canterbury, has American forces onboard, including the American commander of the mission, Captain Jesse Wilson, who has decided to extend his stay on the Canterbury for another week.
The ship is now the headquarters for the Vanuatu leg of the Pacific Partnership.
The exchanges have been hailed as significant in New Zealand-US defence relations.