The No 2 US envoy warned on Friday that the ties between China and Russia are growing and threatening the interests of Washington and its allies, two months before the current administration turns over control of the government to Donald Trump.
Speaking at the Centre for Strategic and International Studies, US Deputy Secretary of State Kurt Campbell also said that US President Joe Biden's administration worked to avert the growing China-Russia partnership, which is "only coming into view" and could have a profound impact on the Ukraine war.
Chinese President Xi Jinping and his Russian counterpart Vladimir Putin have "chosen each other" in the current strategic environment, Campbell said, with China providing support to Russia's defence industrial base.
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"In many respects, these two leaders chose each other and believe they have a lot to offer to one another, and that partnership, while largely hidden and rarely fully unveiled, is animating itself in a number of ways that are going to be deeply concerning," he said.
"I'm not sure that we could have averted or dented or disrupted this growing alliance, but I will also say we tried, and at the ultimate level China and Russia have chosen this path together in ways that will animate global politics that are only now coming into view."
On the Biden administration's handling of US-China relations, he said there is "a growing frustration" on the difficulty to make progress in areas with common interests because of "the profound distrust" from Beijing.
"I myself became increasingly troubled by how difficult even basic kind of interactions were," he said.
"I do believe we're destined for strategic competition, and recognise with the clear eyed sense that, for over a decade, China has believed that the United States is in hurtling decline, and they are determined to try to take steps to replace many elements of American power."
Campbell made his assessment as Biden and his administration prepares to transfer power to president-elect Donald Trump in January.
Trump's return has cast growing uncertainty over Washington's China policy and its strengthening of alliances, a priority during Biden's term.
Concern has mounted in Europe which has been grappling with war on its eastern flank for nearly three years, since Russia's invasion of Ukraine in February 2022. China-Russia ties during this period have been highly scrutinised, as Beijing was accused of supporting Moscow economically as well as transferring dual-use goods that empower Russia's defence industrial base.