Japan, South Korea, Australia and New Zealand are considering holding a four-way summit on the fringes of a NATO leaders gathering in Spain next week, a source close to the South Korean presidential office said Monday.

The envisaged meeting during the NATO gathering is seen by the four nations as an attempt to keep an assertive China in check in the Indo-Pacific after Russia's invasion of Ukraine heightened concerns about a similar event in the region, where Beijing has been expanding its influence.

Japan has sounded out South Korea about the possibility of the quadripartite meeting, the source said.