China is resisting bilateral talks with the United States on nuclear weapons, the US disarmament ambassador told a UN conference on Tuesday, as Washington seeks to advance efforts to reduce nuclear arms stockpiles.

"Despite the PRC's dramatic build-up of its nuclear arsenal, unfortunately it continues to resist discussing nuclear risk reduction bilaterally with the United States," said Robert Wood, referring to the People's Republic of China.

"To date Beijing has not been willing to engage meaningfully or establish expert discussions similar to those we have with Russia. We sincerely hope that will change," he added.

Russia and the United States agreed earlier this year to extend the New START arms control treaty for five years, preserving the last treaty limiting deployments of the world's two largest strategic nuclear arsenals.