Xi Jinping, China’s leader, is reinforcing his bond with President Vladimir V. Putin of Russia. But that could hurt Beijing’s efforts to repair ties with Europe.

Ukrainian drones targeted Moscow for a third day on Wednesday, forcing most of the Russian capital's airports to close hours before Chinese President Xi Jinping was due to fly in for a pomp-filled visit that Kyiv has made clear it opposes.

The Trump administration has said it wants to pull apart Russia and China, but the two countries need each other too much.