That’s according to Peter Orszag, director of the Office of Management and Budget in the Obama administration, who warned in a Washington Post op-ed that Trump’s trade war could expand beyond tariffs.

“Military strategists know a battle can begin in one theater but quickly move into another,” he wrote. “Similarly, what begins as a trade war can evolve into something bigger. It’s a truth worth remembering as the United States imposes substantially higher tariffs on our trading partners, who have the ability to respond in unanticipated ways.”

Trump has imposed tariffs on China and announced duties on steel and aluminum that will go into effect next month. He unveiled tariffs on Canada and Mexico but put them on hold for month. He also directed his administration to study reciprocal tariffs, with potential to enact them in April.

Along the way, he has sown confusion over which tariffs should be taken seriously and which should be been seen as negotiating tactics. But markets are starting to view Trump as more of a “pushover” on tariffs instead of a protectionist, UBS said this past week.

Meanwhile, China has imposed retaliatory tariffs on U.S. energy, agricultural machinery, and certain vehicles. But it has also gone beyond trade by signaling more antitrust scrutiny on U.S. tech companies.

Orszag said another way governments could retaliate is by selling their stockpiles of U.S. debt, as Treasury bonds are a bedrock holding in global financial markets and are widely held around the world.

“This makes Treasury markets a ripe target if negotiations result in prolonged conflict,” he added. “Selling Treasurys would mean taking capital losses, but foreign governments might accept those losses to pressure the United States.”

Foreign entities owned $8.6 trillion in Treasuries as of November, and if just a fraction of that amount was dumped, that could trigger a major selloff on the bond market. And as prices for Treasury bonds fall on the secondary market, yields go up—and drag other borrowing costs, like mortgages, higher too.

At the same time, the U.S. must issue greater volumes of fresh debt to finance the massive budget deficit and redeem earlier debt that’s coming due.

“With debt equal to roughly one-third of gross domestic product maturing in 2025 and needing to be refinanced, additional selling pressure from foreign official creditors unloading their holdings could push interest rates up significantly,” Orszag warned.

Countries retaliating against U.S. tariffs could also reduce their dependence on the Western-backed SWIFT global payment system, he said. After Russia invaded Ukraine in 2022, the West cut off Moscow from SWIFT, but that has encouraged other countries to look for SWIFT alternatives.

Similarly, countries could reduce their reliance on the U.S. dollar in trade and finance, eroding its “exorbitant privilege,” Orszag added.

For now, the greenback is the dominant form of payment in international transactions, and dollar-denominated assets make up the bulk of reserves in global central banks.

But U.S. sanctions on Russia and the freezing of its assets have added momentum to a “de-dollarization” movement as other countries look to shield themselves from dollar vulnerability. That’s helped fuel the massive gold rally as central banks load up on the precious metal to reduce exposure to the dollar.

Economists largely doubt the dollar will lose its dominance anytime soon, but efforts to de-dollarize are piling up, especially from China.

“Though the United States is taking the first shots in the present trade war, other fronts are likely to open, and it is crucial to understand where skirmishes could occur,” Orszag said. “It’s true that other countries have much to lose from a trade war. But so does the United States, especially as it’s unlikely to remain contained to trade alone.”