President Donald Trump accused Russia and China on Monday of devaluing their currencies while the United States raises interest rates.

Trump’s tweet referred to what he sees as unfair trading advantages: if a country’s currency is artificially low, its exports are more competitive. Higher U.S. interest rates would generally increase the value of the dollar, making U.S. exports more expensive.

Since Trump took office in January 2017, the dollar has weakened substantially against most currencies, including the Chinese yuan and, until the United States imposed sanctions on Russia in the last few weeks, the ruble.

Against the yuan, the dollar has fallen by 8.6 percent since Jan. 20, 2017, while it has appreciated 4.5 percent against the ruble. Until the United States announced sanctions on Russian oligarchs earlier this month, however, the dollar had weakened by nearly 4 percent against the Russian currency. That gain was entirely erased by a two-day drop of 8.4 percent in the ruble on April 9 and 10.

More widely, the U.S. dollar index, which measures the greenback’s value against a basket of major trading partner currencies, has declined by 11.2 percent since Trump became president.

The U.S. Treasury, in a semiannual report on Friday, again refrained from naming any major trading partners as currency manipulators. The report came as the Trump administration pursues potential tariffs, negotiations and other restrictions to try to cut a massive trade deficit with China.

The report did not mention Trump’s recent threats to impose billions of dollars worth of tariffs on Chinese goods over Beijing’s intellectual property practices, or pending Treasury restrictions on Chinese investment in the United States.

White House spokeswoman Sarah Sanders later told reporters aboard Air Force One on a trip by the president to Miami that China is on a U.S. Treasury Department watch list for being potentially labeled a currency manipulator.