During a joint fishery patrol in the South Pacific last week, a U.S. Coast Guard cutter requested permission to call in the Solomon Islands – and was denied. The cutter USCGC Oliver Henry had a scheduled replenishment port call in Honiara, intended to enable its mission to help the Solomons prevent illegal fishing. A Coast Guard press officer told Reuters that Solomons officials “did not respond” to a request to enter port, so the vessel diverted about 500 nm from its course to call in Papua New Guinea instead.

The unusual snub follows months after the Solomons government signed a security pact with China, which allows Beijing to stage forces on the island nation’s territory. A leaked draft of the agreement suggests that it will also allow Chinese naval vessels to call for replenishment at Honiara. The deal has raised serious concerns for officials in the U.S. and Australia, since the Solomon Inslands are a natural jumping off point for military operations in the Coral Sea and the South Pacific. In WWII, the U.S. had to engage in a fierce fight to dislodge Japanese forces from the Solomons, and the islands’ strategic location is well-remembered.

The diplomatic brush-off may also have extended to the Oliver Berry’s partner vessel, the Royal Navy patrol ship HMS Spey. The Royal Navy would not confirm whether or not Spey had been turned away, saying only that it is “routine practice” for itineraries to change.

A spokesperson for the Coast Guard told the AP that the U.S. State Department is in dialogue with the Solomons government, and that in future it expects that clearances will be provided for American ships.

HMS Spey, Oliver Berry and personnel and assets from 15 other nations were in the area as part of Operation Island Chief, one of four annual patrols focused on deterring illegal fishing. It was the first time the Royal Navy had joined the 10-day mission.