It used to be regarded as the worst thing that could happen to the U.S. in the foreign policy sphere if Russia (or the U.S.S.R.) formed an alliance with China. From Ray McGovern at consortiumnews.com:
Xi Jinping’s reception of Putin yesterday in Beijing sealed the increasingly formidable strategic relationship, fundamentally misunderstood in Washington.

Russian President Vladimir Putin and Chinese President Xi Jinping and their teams meeting in Beijing on Thursday. (Konstantin Zavrazhin, Kremlin)
Chinese President Xi Jinping’s extremely warm reception of President Vladimir Putin yesterday in Beijing sealed the increasingly formidable Russia-China strategic relationship. It amounts to a tectonic shift in the world balance of power.
The Russia-China entente also sounds the death knell for attempts by U.S. foreign policy neophytes to drive a wedge between the two countries. The triangular relationship has become two-against-one, with serious implications, particularly for the war in Ukraine. If U.S. President Joe Biden’s foreign policy geniuses remain in denial, escalation is almost certain.
In a pre-visit interview with Xinhua, Putin noted the “unprecedented level of strategic partnership between our countries.” He and Xi have met more than 40 times in person or virtually. In June 2018, Xi described Putin as “an old friend of the Chinese people” and, personally, his “best friend.”
For his part, Putin noted Thursday that he and Xi are “in constant contact to keep personal control over all pressing issues on the Russian-Chinese and international agenda.” Putin brought along Defense Minister Andrey Belousov as well as veterans like Foreign Minister Sergey Lavrov and key business leaders.