New Delhi, Nov. 4 -- In diplomacy, even short words matter. And with a brief Truth Social post, President Donald Trump may have revealed his approach to the U.S.-China relationship - to the delight of reputation-conscious Beijing but to the worries of U.S. allies concerned with China's ascending global power.

"The G2 WILL BE CONVENING SHORTLY!" Trump wrote moments before he headed into a widely watched summit with Chinese leader Xi Jinping on Oct. 30 in South Korea, reviving a phrase that dates to the early 2000s but had been rejected by Washington for at least the past decade - including during Trump's first term.

G2, or Group of Two, was first proposed by American economist C. Fred Bergsten in 2005 to urge what he considered the neces...