The phrase the geopolitical posse has settled on is "debt book diplomacy." If you search for that phrase the only links you see are about China. The example the think tanks are currently freaking balls about is Vanuatu which has traditionally traded largely with Australia.

Australia voiced concerns a few months ago that Vanuatu was slowly sliding into China’s orbit. In April, Fairfax Media, citing unnamed senior Australian defense officials, reported that China and Vanuatu were in discussions on a potential Chinese military base in the country. Both sides denied the report – Vanuatu quite angrily. What is undeniable, however, is that China has sought to become a major player in Vanuatu. China owns almost half of the country’s $440 million in foreign debt. A U.S. State Department report identified Vanuatu as one of 16 states that China was aiming to control via “debtbook diplomacy.” And since 2007, trade between China and Vanuatu has increased by a factor of six – Vanuatu actually imported more last year from China than from Australia.

(Geopolitical futures, paywalled)

A military base on Vanuatu would be the South Pacific equivalent of a Soviet military base on Cuba as far as our current trade and military alliances go.