US National Security Advisor Jake Sullivan says the leaders of the United States, Japan and South Korea will meet on Wednesday to discuss North Korea's nuclear and missile development.

Sullivan told reporters on Tuesday that US President Joe Biden, Japanese Prime Minister Kishida Fumio and South Korean President Yoon Suk-yeol will hold talks on the sidelines of a NATO summit in Madrid.

Sullivan said the leaders' first meeting "will be mainly focused on the continuing threat" from North Korea.

He also said they will discuss "what we can do on the economic pressure side, particularly when it comes to depriving the North of hard currency that they use to fund their nuclear and missile programs."

This will be the first meeting between the leaders of the three countries since September 2017.