New Zealand Prime Minister John Key is to lead a Parliamentary delegation to the Pacific island nation of Samoa next week to mark the 50th anniversary of the Treaty of Friendship between the two nations.

"Samoa is the only country in the world with which New Zealand has a formal Friendship Treaty it's a mark of our deep ties, shared values and long history of cooperation," Key said in a statement Monday.

"New Zealand and Samoa's relationship is a special one, and the Treaty of Friendship, signed shortly after Samoa gained independence from New Zealand in 1962, is the cornerstone of that relationship."

Key would meet with Prime Minister Tuilaepa Sailele Malielegaoi and members of his Cabinet and discuss regional issues of mutual interest ahead of this year's Pacific Islands Forum.

Key would be accompanied by representatives of all the political parties in the New Zealand Parliament on the visit, which would include a state luncheon at the Robert Louis Stevenson Museum, where the Treaty of Friendship was signed.

Key would also launch Friendship Week, which comprises a range of events including a New Zealand film and television festival, a food and beverage mini-expo, and a series of cultural events and exhibitions.

He would depart from Wellington on July 31 and return to New Zealand on Aug. 1.

As part of the celebrations New Zealand is also sending the Rugby World Cup trophy, which it currently holds, to Samoa this week.

Foreign Affairs Minister Murray McCully announced Friday that the Webb Ellis Cup, won by New Zealand's All Blacks when they hosted the tournament last year, would travel with cup-winning All Blacks coach Sir Graham Henry and player Victor Vito.