Foreign Minister Murray McCully will make the announcement this afternoon.
Mr Moore would replace career diplomat Roy Ferguson in the role.
Mr Moore entered Parliament in 1972 when he was elected to represent Mt Eden in Auckland and he later represented seats in Christchurch.
In government he held several ministerial positions and was involved in trade negotiations. In 1990 he became leader of the Labour Party and was prime minister a few months replacing Geoffrey Palmer. Labour lost the next election and Mr Moore was Opposition leader for three years.
In 1999 he was elected director-general of the World Trade Organisation. However, he served only half the usual six-year term -- finishing up in 2002 under a deal with his rival and successor Supachai Panitchpakdi.
Mr Moore was highly regarded in the role and restored confidence in the body while advancing international trade negotiations. His trade background will be valuable as New Zealand seeks to progress on the US joining the Trans Pacific Strategic Economic Partnership (TPP). If successful that agreement would enable New Zealand to have a trade deal with the US along with partners Brunei, Chile and Singapore.
Prime Minister John Key is to visit Washington this year.
Another former prime minister -- Jim Bolger -- has also previously served as New Zealand's ambassador to the US.
