HONG KONG — Global trade has been upended again after the Supreme Court struck down President Donald Trump’s “reciprocal” tariffs, with U.S. trading partners and businesses around the world grasping to understand the system that replaces them.

A new flat global tariff of 10% paid by U.S. importers took effect Tuesday, lower than the 15% that Trump said he would implement days before. Under Section 122 of the Trade Act of 1974, the 10% tariff can remain in place for 150 days without congressional approval.

China is the “biggest winner” from the Supreme Court ruling, with an effective U.S. tariff rate now much closer to that of other countries, said Alicia García-Herrero, chief economist for Asia-Pacific at French investment bank Natixis.

Among other benefits, China’s lower tariff rate reduces the incentive for companies to shift production to other countries in Asia, at least temporarily.

But the whiplash has created overwhelming uncertainty for key U.S. allies and some of Washington’s biggest trading partners, many of whom had already announced or were nearing trade deals with the U.S., some having offered major concessions with the aim of securing favorable rates under Trump’s now-defunct tariff regime.

In Asia, Trump administration officials had rushed to conclude deals in the weeks before the court ruling, with Indonesia agreeing to a 19% tariff rate only a day earlier.

The tariff ruling also comes just weeks before Trump’s upcoming trip to China, where he hopes to maintain a delicate trade truce with the world’s second-biggest economy.

Those who stand to lose the most include Japan and Taiwan, both of which had previously pledged hundreds of billions in U.S. investment in exchange for a tariff rate of 15%. Singapore and Australia also stand to lose since they already had a relatively favorable tariff rate of 10%.

“If you’re Taiwan, you’re like, why on earth did I commit to $250 billion if I’m getting the same tariffs?” said García-Herrero, who is based in Hong Kong.

The Trump administration has said that it will stand by existing deals and that it expects U.S. trading partners to do so as well.

“The good news is that almost all countries and corporations want to keep the deal that they already made,” Trump said Tuesday in his State of the Union address, “knowing that the legal power that I as president have to make a new deal could be far worse for them.”

A day earlier, Trump said in a social media post that any countries that tried to “play games” with trade deals after the court ruling would be hit with much higher tariffs.

Major trading partners in Asia, highly dependent on U.S. exports, are generally sticking within the terms of their existing deals or taking a wait-and-see approach.

India, which had planned to sign an agreement in March, delayed a scheduled trade delegation visit to Washington last week, saying talks would resume once there was more clarity. Its trade minister then had a surprise lunch meeting in New Delhi on Thursday with Commerce Secretary Howard Lutnick.

While Trump officials say they expect the deals to be maintained, “point one of every deal is the reciprocal tariff rate,” said Deborah Elms, head of trade policy at the Hinrich Foundation in Singapore.

The primary question for many governments, she said, is whether their goods are now subject to their previous rates or the new 10% rate, which the White House has not clarified.

“That right there is causing a fair amount of anxiety over what is the actual rate, and then what happens to the rest of the agreement,” Elms said.

U.S. Trade Representative Jamieson Greer said last week that for some countries, which he did not name, tariff rates would rise to 15% or even higher while remaining compatible with existing deals.

He says that there are no plans to raise tariffs on Chinese goods ahead of Trump’s trip to China, which the White House says will begin March 31, and that he does not expect the Supreme Court ruling to affect Trump’s meeting with Chinese President Xi Jinping.

China, which responded to Trump’s first reciprocal tariffs last year with mounting tariffs of its own, said after the ruling that it would “comprehensively assess” any future U.S. tariff changes and adjust its countermeasures as appropriate.

“The current situation has placed China in a relatively comfortable position,” Chinese international affairs commentator Qiu Zhenhai said in a social media post.

“This is because Trump’s proposed high tariffs — whether directed at the world or specifically at China — are currently being constrained by supreme legal authorities internally and, frankly speaking, have triggered significant backlash within the United States.”

But China still has a lot to worry about, such as Trump’s ability to impose export controls on strategically vital products such as semiconductor chips.

According to Greer, one of the main ways the Trump administration plans to replace the reciprocal tariffs is through investigations, permitted under Section 301 of the 1974 Trade Act, of countries accused of treating the U.S. or its companies unfairly.

Elms said those investigations, along with national security probes focused on strategic industries under the same law, could provide the White House with a more solid basis to impose fresh tariffs, as well as other punitive measures that could end up being far worse for some countries than the tariffs previously struck down.

Though Greer has indicated a desire to move swiftly on Section 301 investigations, it would be difficult to exclude China from any list of countries facing investigations, which would risk antagonizing Beijing before Trump’s trip, Elms said.

Greer said his office was also continuing an existing Section 301 investigation into China that stems from Trump’s first-term trade deal with Beijing and could be used to justify steep new tariffs.

China said last week that it had “earnestly fulfilled its obligations” under that deal.

The Supreme Court ruling also did not affect sector-specific U.S. tariffs on automobiles and steel, which are crucial industries for China, as well as South Korea and Japan.

On Tuesday, the president of Hyundai Motor, one of South Korea’s biggest carmakers, urged lawmakers to swiftly approve the $350 billion in pledged U.S. investment, citing the risk of higher sectoral tariffs.

Elms said that many U.S. trade partners will “have domestic politics of their own” to consider.

She added: “It’s really getting very challenging to manage a government-to-government relationship with the U.S. and we will see some of that irritation, I think, spill over as the tariff rates keep changing and these deals appear to be more or less desirable.”