The action is mostly symbolic, requiring the administration to consult with the International Monetary Fund to try to eliminate the unfair advantage the currency measures have given a country. But China is likely to view the label as a rebuke, further escalating pressures between the countries.

The move will finally fulfill Mr. Trump’s campaign pledge to designate China a currency manipulator. As a presidential candidate, Mr. Trump was sharply critical of China’s currency practices and promised to label China a manipulator if elected.

Until Monday, Mr. Trump’s Treasury had declined to apply the label to China in the five currency reports it issued since the president took office. Instead, it has said the United States has deep concerns about China’s intervention in its currency.

Economists say that China held down the value of its currency for many years, but it had already ceased that practice by the time Mr. Trump came into office. Ultimately, Mr. Trump was persuaded by his advisers to hold off on the label. In its most recent currency report, in May, the Treasury Department criticized China’s trade and currency practices but still did not conclude that Beijing was improperly devaluing its currency.

The hardened positions underscore the increasingly tough path to resolving the trade dispute, which has begun to inflict damage across the global economy. American and Chinese negotiators met in Shanghai last week, the first face-to-face discussions since trade talks collapsed in May, but made little progress in resolving their differences.

The question now is whether Beijing will allow its currency to weaken further and what Mr. Trump may do in response. The two sides have been locked in an intractable tit-for-tat economic war, with China meeting Mr. Trump’s tariffs with punishment of its own.

The United States has already imposed tariffs on $250 billion worth of Chinese goods, placed tougher restrictions on Chinese investment, banned some Chinese companies from doing business with American companies and begun restricting visas for Chinese graduate students in sensitive research fields like robotics and aviation. Those moves were aimed at getting China to open its markets to American companies, protect American intellectual property and buy more agricultural products, none of which have happened yet.