A doubling of American tariffs on Chinese goods. Nationalist Chinese bloggers comparing President Trump’s levies to a declaration of war. China’s Foreign Ministry vowing that Beijing will “fight to the end.”

For years, the world’s two biggest powers have flirted with the idea of an economic decoupling as tensions between them have risen. The acceleration this week, in both actions and words, of their trade relationship’s deterioration has made the prospect of such a divorce seem closer than ever.

On Wednesday, the Trump administration carried out its threat to increase tariffs on Chinese exports by an additional 50 percent unless China rescinded its own retaliatory tariffs on U.S. goods from last week. The minimum tax on Chinese imports is now a staggering 104 percent.

With China’s top leader, Xi Jinping, and Mr. Trump locked in a game of chicken — each unwilling to risk looking weak by making a concession — the trade fight could spiral out of control, inflaming tensions over other areas of competition like technology and the fate of Taiwan, the self-governing island claimed by Beijing.

Mr. Trump’s bare-knuckle tactics make him a singular force in U.S. politics. But in Mr. Xi, he faces an opponent who survived the turmoil of China’s late-20th-century political purges, and who views the United States’ competitive tactics as ultimately aimed at subverting the ruling Communist Party’s legitimacy.