WELLINGTON, New Zealand » A U.S. Navy warship will visit New Zealand next month for the first time since the 1980s, ending a 30-year-old military stalemate between the countries that was triggered when New Zealand banned nuclear warships.

New Zealand Prime Minister John Key announced Tuesday that he had given clearance for the destroyer USS Sampson to visit during celebrations marking the Royal New Zealand Navy’s 75th anniversary.

The visit marks a continued thaw in military relations, which turned frosty when New Zealand enacted its nuclear-free policy in the mid-1980s.

The policy prevents ships that have nuclear weapons or are nuclear powered from visiting. Because the U.S. won’t officially confirm or deny if its ships have nuclear capabilities, New Zealand had imposed a blanket ban on U.S. ships.

But Key said he’d taken advice from his own officials and was “100 percent confident” the USS Sampson wasn’t nuclear powered or carrying nuclear weapons.

“I think it’s a sign of the fact that the relationship between New Zealand and the United States is truly in the best shape it’s been since the anti-nuclear legislation was passed,” Key said. “All of those last vestiges of the dispute that we had have really been put to one side.”

Key said he didn’t think the result of the upcoming U.S. presidential election would affect the relationship.

The dispute began in 1985 when the New Zealand government refused to allow a U.S. destroyer to visit. The U.S. responded by downgrading its military ties. New Zealand passed its nuclear-free law in 1987.

The relationship improved after 2001, said Rear Admiral John Martin, the chief of the New Zealand Navy, when New Zealand agreed to send special forces and later a reconstruction team to Afghanistan. The U.S. and New Zealand signed defense agreements in 2010 and 2012.

“We’ve been working with the U.S. Navy for many decades and we’re looking forward to hosting them down here,” Martin said. “A birthday is not complete without your friends.”

Mark Gilbert, the U.S. ambassador in Wellington, said the visit helped clarify the improvement in the relationship. He said the U.S. and New Zealand shared similar values and had much in common, from culture to tourism.

“We’re all very excited,” Gilbert said.