The buck stops with Donald J. Trump. The president-elect, who has developed an early knack for challenging U.S. corporations via Twitter, reserved his most biting comments for the U.S. dollar, which vaulted 4% higher at its peak in the wake of the real estate billionaire’s Nov. 8 election victory over Hillary Clinton.

In a Friday interview with The Wall Street Journal, Trump said the U.S. currency, which touched a more-than 14-year high about two weeks ago, has gotten “too strong,” especially considering the China’s yuan USDCNY, -0.12% is “dropping like a rock.” “Our companies can’t compete with them now because our currency is too strong. And it’s killing us,” he told WSJ.

Read: Trump is waving adios to the longstanding Trump ‘strong dollar policy’

Trump’s remarks about the dollar underscore the soon-to-be president’s unconventional political style, and could threaten to roil stocks, which have enjoyed a robust run higher in recent months. Presidents rarely offer their direct view on the strength or weakness in U.S. currency for fear of influencing the market. The remarks, part of a sweeping discussion, including on the topic of a House Republican corporate tax plan, raises more concerns about Trump’s agenda and sets the scene for clashes within his own party—a scenario that could make it challenging for him to achieve his broad policy goals.

Check out: Trump says core part of House GOP corporate-tax plan is ‘too complicated’

Expectations for pro-business policies under a Trump administration has supported the buck’s ascent, which had been underpinned by anticipation that the Federal Reserve would seek to normalize interest-rate policy. That normalization amid more muted growth in the rest of the world has made the dollar an appealing bet for traders. Fortifying its strength, Trump also has talked about a litany of legislative initiatives, including increased fiscal spending and tax cuts, that could accelerate U.S. economic growth. That cocktail helped catapult the dollar in 2016.

Although concerns about Trump’s ability to follow through with an ambitious economic agenda has resulted in gains being pared in many of the assets that moved the most following his win, advances are still strong. The buck as measured by the ICE U.S. Dollar Index DXY, -0.11% , has lost 1.8% so far in January but is still up about 2.4% since November and up about 1.4% over the past 12 months, according to FactSet data. The U.S. market was closed on Monday in observance of Martin Luther King Jr. Day.

A strong dollar usually implies that the U.S. economy is in a solid footing but it can also result in headwinds for U.S. companies. For corporations that do a large portion of their business overseas, a beefier buck means lower sales when the money is repatriated from a country with a weaker currency.

So far, the action in the stock market suggests that investors are betting that growth will overcome any headwinds of a rising dollar. On the stock front, the Dow Jones Industrial Average DJIA, -0.46% , which is slogging toward the psychologically important milestone of 20,000, has advanced 8.2% since the election, while the S&P 500 index SPX, -0.84% has gained 6% and the Nasdaq Composite Index COMP, -1.26% has ratcheted 6.7% higher.

The path of the dollar and coming corporate quarterly results will likely prove the most influential factor for equities.

However, exactly how Trump’s recent statements will translate into policy is hard to guess. Wall Street heavyweights like DoubleLine Capital’s Jeff Gundlach are thinking hard about the implications of Trump policy.

“Is it really a given that Trump will bring us a strong dollar, if he is supposed to be helping the forgotten middle class?” Gundlach said during a recent interview with Barron’s.

During a Tuesday morning interview on CNBC in Washington, outgoing Treasury Secretary Jacob Lew failed to offer his opinion on the dollar, but suggested that the U.S. economy is in better shape than it was in 2008 and indicated that a stronger dollar is good if it also is backed by healthy growth and a strong labor market.

Trump will be sworn in on Friday.