In a break with over two decades of strong dollar policy, President-Elect Donald Trump told the Wall Street Journal “Our dollar is too strong.” He was especially concerned about how the strong dollar has put the U.S. at a competitive disadvantage with China.

Traditionally, the U.S. government has favored a strong dollar to bolster confidence in the U.S. economy and securities markets, to restrain inflation and thus keep interest rates low, as well as to enhance the buying power of American consumers and businesses on world markets, the Journal says.

The U.S. dollar has risen about 25% versus a basket of currencies since 2014, the Journal reports. After the election, it rose about 4%, but Trump’s recent comments have sparked a subsequent pullback. The New York Times reports a 1% decline in the value of the dollar versus an index of major currencies as of Tuesday, as well as a 1.5% increase in the dollar price of gold on world markets. Even weakened currencies such as the Mexican peso and the Turkish lira rose versus the dollar, the Times reports. See also: (What Drives the Price of Gold?)

Dangerous Talk

In discussing the established U.S. policy of not commenting on the value of the dollar, University of California, Berkeley economics professor Barry Eichengreen told the Journal that talking “about the value of the single most important price in the global economy in terms that could be misunderstood can wreak havoc with markets.” Another observer who fears that Trump runs the risk of destabilizing markets by commenting on this issue is former Treasury Department economist Tim Duy, according to the Journal.

Besides talk, the president also has the power to order foreign exchange interventions by the U.S. government, the Journal notes. These are purchases or sales of foreign currency reserves undertaken to influence the value of the dollar.

Some previous U.S. presidents have taken a central role in dollar policy, which is a nuanced political and financial art usually left to the Secretary of the Treasury.

Past Policy Shifts

In 1971, President Richard Nixon unexpectedly announced that the dollar would no longer be backed by gold, a move that put world markets in turmoil, until floating exchange rates became accepted as the new normal, the Journal notes.

In the early 1980s, a strong dollar led to a situation similar to today, with rising talk of protectionism and tariffs to curb imports to bolster U.S. industry. The result was the Plaza Accord with the U.K., Germany, France and Japan, which restrained the dollar’s rise, spurred trade, and reduced currency manipulation.

The situation in 2017 might result in a similar currency deal, the Journal reports.

Emerging Markets Risk

Besides increasing the U.S. trade deficit, a strong dollar over an extended period can increase the risk of an emerging markets crisis, the Times notes. If falling currencies prompt massive selling of investments in emerging markets, a full-blown crisis may ensue. The last crisis was 15 years ago, and the current precipitous fall in the Turkish lira and capital outflows from China may be warning signs of another in the making, said currency specialist Jens Nordvig at Exante Data, as cited by the Times.