The head of the US marines has raised the prospect of future training missions in Vietnam - the latest sign of a deepening strategic relationship between Hanoi and Washington that is being closely watched in Beijing.
Marine Corps commandant General Jim Amos was quoted this week in the Marine Corps Times newspaper as saying that an upcoming bomb disposal effort in Vietnam could lead to the country being used for training.
"We are not training in Vietnam," Amos said of the deployment in July that will see US marines teach locals how to dispose of thousands of bombs left over from the Vietnam war.
"But I would hope that someday down the road, with relationships we build over the next year or two, that we'll be able to train in Vietnam, perhaps with air forces, and operate along with them."
Chinese officials have been eyeing warily the emerging relationship between the once bitter enemies, with incoming president Xi Jinping having warned Vietnamese officials about the relationship.
The military relationship has seen limited naval exercises, air force exchanges and visits by US naval vessels to the strategic Cam Ranh Bay for repairs. But weapons sales remain restricted, despite Vietnamese pressure, and diplomatic efforts to formalise a strategic partnership have stalled amid ongoing US concerns over human rights in the Communist Party-ruled state. Hanoi has jailed dozens of dissidents in recent weeks, despite releasing two others amid US protests.
Professor Carl Thayer, a scholar on the Vietnamese military at the Australian Defence Force Academy, said the July move would be significant but he did not believe a full marine training mission would be accepted in the current environment.
"That may be their aspiration in the long term, but frankly there is not yet a China threat big enough to justify it … it would simply be too provocative."
Such a deployment would carry historical baggage, as marines played a key role in the Vietnam war. Hanoi officials have not commented on the report.
US marines are expanding their reach in Asia Pacific, with Okinawa-based troops set to train in Guam, Australia and possibly the Philippines this year.
Naval officials, meanwhile, confirmed this week that the first of four new littoral combat ships, designed to work with marines and to be based in Singapore, would arrive next month.