Vietnam and the United States are to hold joint naval activities next month but they were long-planned and are unconnected to regional tensions in the South China Sea, the US Navy said Thursday.

The event in the central Vietnamese city of Danang next month will last about one week and is "not an exercise" because there is no combat training, said Lieutenant Commander Mike Morley, a navy spokesman.

"There's no connection at all" with territorial disputes simmering in the South China Sea, he said. "It's merely just a coincidence of timing."

At least one US Navy destroyer and a diving and salvage ship are likely to arrive in Danang for the mission, known as "naval exchange" activities, he said.

The two sides will cooperate in medical and dental clinics and a "tabletop" search and rescue scenario, while sailors will perform community service work.

A similar programme took place for the first time last year, Morley said, describing it as part of the "natural progression" of ties between the two militaries.

Former wartime enemies the US and Vietnam normalised relations in 1995 and have been rapidly building relations across a wide range of areas -- in part due to a spike in tensions between Beijing and Hanoi.

Vietnamese foreign ministry spokeswoman Nguyen Phuong Nga told reporters the annual event would "promote relations between the two navies, carry out humanitarian activities and exchange concerning professional matters, as well as search and rescue operations."

Tensions between China and other claimants to strategically important waters in the South China Sea -- home to two potentially oil-rich archipelagoes, the Paracels and the Spratlys -- have escalated in recent weeks.

Since late May Vietnam has twice accused China of violating its 200-nautical-mile exclusive economic zone and interfering with oil survey ships.

Nga said Vietnam was not aware of any further incidents, and reiterated the country's resolve to settle disputes "through peaceful means based on international law".

Chinese state media said Thursday that China and Vietnam conducted two days of joint naval patrols earlier this week in the Gulf of Tonkin as part of an annual plan of "friendly exchanges" between the two militaries.

On Wednesday China reportedly warned the United States to stay out of the maritime spat.