The leaders of the United States, Japan, India and Australia held virtual talks on Friday. 

In the first summit of the so-called Quad countries, the four sides discussed cooperation to boost security and respond to threats in the Indo-Pacific region.

Their joint response is likely targeting China, though the threat was not specified.

The leaders are known to have addressed various China-related issues during the closed-door meeting, such as COVID-19, climate change, cyber security and the economy.

They also agreed to financially support an Indian pharmaceutical firm to produce one billion COVID-19 vaccine doses by the end of next year, a move seen as vaccine diplomacy against China.

In a joint statement, the Quad leaders also reaffirmed their commitment to the complete denuclearization of North Korea in accordance with UN Security Council resolutions.

The Quad forum was first launched to respond to the Indian Ocean earthquake and tsunami in 2004. Three rounds of foreign ministerial talks have been held since 2017.

The four leaders agreed to hold face-to-face talks within the year and also strengthen communication between their countries' top diplomats.