The five nations in the world's leading intelligence-sharing network have been exchanging classified information on China's foreign activities with other like-minded countries since the start of the year, seven officials in four capitals said.
The increased cooperation by the Five Eyes alliance — grouping Australia, Britain, Canada, New Zealand and the United States — with countries such as Germany and Japan is a sign of a broadening international front against Chinese influence operations and investments.
Some of the officials, who spoke on condition of anonymity because of the sensitivity of the talks, said the enhanced cooperation amounted to an informal expansion of the Five Eyes group on the specific issue of foreign interference.
While China has been the main focus, discussions have also touched on Russia, several said.
"Consultations with our allies, with like-minded partners, on how to respond to China's assertive international strategy have been frequent and are gathering momentum," a U.S. official told Reuters. "What might have started as ad hoc discussions are now leading to more detailed consultations on best practices and further opportunities for cooperation."
All the governments involved, including Germany and Japan, declined to comment.
China, faced with a growing backlash from Washington, Canberra and other capitals, has rejected accusations that it is seeking to influence foreign governments and that its investments are politically driven.
The enhanced coordination by the Five Eyes network suggests that, despite signals from U.S. President Donald Trump that he is prepared to go it alone in the confrontation with China, members of his administration are working hard behind the scenes to put together an informal coalition to counter Beijing.
It also represents another blow to China's fading hopes of convincing European countries, unsettled by Trump's "America First" policies, to distance themselves from Washington and move closer to Beijing.