China has played down this week's U.S. decision to lift a decades-old ban on sales of lethal arms to Vietnam as it looks to avoid aggravating relations already strained by territorial disputes in the South China Sea.

On Tuesday, a day after U.S. President Barack Obama expressed his desire to begin a new era of closer economic and military ties with Vietnam, the vice foreign ministers of China and Vietnam met in a Chinese border province to discuss their relationship.

"China and Vietnam are friendly neighbors connected by mountains and rivers," said Chinese Foreign Ministry spokeswoman Hua Chunying at a news conference Tuesday. China, Hua said, is willing to work with Vietnam to implement a range of legal agreements "to elevate boundary management and cooperation."