Over three months, senior Biden administration officials held half a dozen urgent meetings with top Chinese officials in which the Americans presented intelligence showing Russia’s troop buildup around Ukraine and beseeched the Chinese to tell Russia not to invade, according to U.S. officials.

Each time, the Chinese officials, including the foreign minister and the ambassador to the United States, rebuffed the Americans, saying they did not think an invasion was in the works. After one diplomatic exchange in December, U.S. officials got intelligence showing Beijing had shared the information with Moscow, telling the Russians that the United States was trying to sow discord — and that China would not try to impede Russian plans and actions, the officials said…

The growing alarm among American and European officials at the alignment between China and Russia has reached a new peak with the Ukraine crisis, exactly 50 years to the week after President Richard M. Nixon made a historic trip to China to restart diplomatic relations to make common cause in counterbalancing the Soviet Union. For 40 years after that, the relationship between the United States and China grew stronger, especially as lucrative trade ties developed, but then frayed due to mutual suspicions, intensifying strategic competition and antithetical ideas about power and governance.

In the recent private talks on Ukraine, American officials heard language from their Chinese counterparts that was consistent with harder lines the Chinese had been voicing in public, which showed that a more hostile attitude had become entrenched, according to the American accounts.