New Zealand Foreign Minister Murray McCully said he discussed the disputed South China Sea with a "charming" Philippine President Rodrigo Duterte during an informal meeting late Tuesday.

McCully said the pair had a wide-ranging discussion but declined to comment on whether Duterte's controversial drug crackdown was discussed.

They spoke during Duterte's overnight stopover in Auckland, New Zealand's largest city, on his way back from the Asia-Pacific Economic Cooperation summit in Peru.

"He's a tough guy but he was warm, courteous and actually quite charming," McCully told the New Zealand Herald after the meeting. "He doesn't beat around the bush. He has got quite firm views and he expresses them, and very colorfully."

Police and vigilante groups have killed more than 2,400 people in the Philippines since Duterte vowed to crack down on drug dealers when he took office in June, attracting criticism from human rights watchdogs, the United States and the United Nations.

The meeting in Auckland comes at a tense time for relations between the Philippines and the United States, its strongest Western ally. Duterte has made repeated threats and verbal tirades against the United States, a significant donor, and is making overtures to Russia and to China.

Duterte lashed out at Western "bullying" and "hypocrisy" during his first meeting with Russian President Vladimir Putin in Peru on Saturday and said the United States could not be trusted when it came to alliances.

Adham Crichton, a spokesman for McCully, said on Wednesday there would be no further comment on the Auckland discussions because it was not a formal bilateral meeting.

China is at odds with a number of its Asian neighbors, including the Philippines, over disputed claims in the South China Sea, through which $5 trillion in ship-borne trade passes every year.