Trump turns up the heat. China says bring it on.

In the past week alone, Trump has placed tariffs on China, Mexico and Canada, the U.S.’s three biggest trading partners, and readied measures to challenge China’s dominance in shipbuilding. On Friday, the president upended U.S. foreign policy by opening talks with Russia to end the war in Ukraine—a move that some believe could be aimed at driving a wedge between Moscow and Beijing.

On Wednesday, China’s leaders signaled that it hasn’t been thrown off by the dramatic developments in Washington. Instead, Beijing is as determined as ever to become self-sufficient and impervious to Western pressure.

“If war is what the U.S. wants, be it a tariff war, a trade war or any other type of war, we’re ready to fight till the end," Chinese Foreign Ministry spokesman Lin Jian said after the latest exchange of retaliatory tariffs. “Intimidation does not scare us. Bullying does not work on us. Pressuring, coercion or threats are not the right way of dealing with China. Anyone using maximum pressure on China is picking the wrong guy."

Beijing sent a similar, albeit more calibrated message, at the opening of China’s annual legislative session on Wednesday, where it set an ambitious goal to expand its economy by around 5% this year, unchanged from last year, suggesting that it doesn’t see its growth trajectory being derailed by Trump’s actions.

It also unveiled plans to increase military spending by 7.2%, continuing a military buildup to support its increasingly dominant posture in the region. Though its defense budget is less than half that of the U.S., its spending far surpasses that of other countries in its region, totaling more than the combined budgets of the next 22 largest militaries in the region, including India, Japan and South Korea, according to an analysis by the Center for Strategic and International Studies’ China Power Project.

In recent weeks, China’s military has stepped up the tempo of air and naval drills across the region, including around the island of Taiwan, which it claims as its own territory, and off the east coast of Australia, where it conducted a live-fire drill last month. Beijing has increasingly joined hands with Moscow to conduct sailings around the main island of U.S.-allied Japan and joint air and sea exercises off the coast of Alaska.

During Wednesday’s gathering at Beijing’s Great Hall of the People, senior leaders championed homegrown technological talent that it has long hoped will allow China to catch up—or surpass—the U.S. technologically.

Premier Li Qiang, China’s No. 2 leader, devoted sections of his annual government work report to Chinese innovation, which got a boost earlier this year from DeepSeek, an artificial intelligence-powered chatbot that has upended global assumptions about the dynamics of the global AI race.

And in response to additional 10% tariffs the Trump administration has placed on Chinese imports, Beijing presented a raft of retaliatory measures meant to sting the U.S.

Trump’s return to office has stiffened Beijing’s resolve to strengthen its hand at home, particularly as slowing growth opens up potential vulnerabilities, says Andrew Batson, China research director for Gavekal Dragonomics.

“The stated strategy of the Chinese government is import substitution," Batson said. “They say, ‘We need to reduce imports, we need to increase self-reliance and reduce reliance on foreign technologies and foreign inputs.’"

On Wednesday, Li underlined the importance of self-reliance and boosting spending from households and businesses, framing increased consumption as part of a program that would keep the domestic economy humming while ensuring a market for the homegrown companies that he is hoping to nurture.

The urgency of the effort could be seen in the premier’s invocation of the rising threats to Beijing’s position amid what he called “an increasingly complex and severe external environment."

On Tuesday, weeks after Trump used his inaugural address to rail against Chinese-linked ports at either end of the Panama Canal, a consortium of investors led by BlackRock said it would buy majority stakes in both ports from Hong Kong-based conglomerate CK Hutchison, putting U.S. firms in control.

“We didn’t give it to China, we gave it to Panama, and we’re taking it back," Trump told Congress during an address hours later.

China’s growing reliance on exports has left its economy particularly exposed in a world of Trumpian trade wars and tariffs. Last year, exports accounted for nearly one third of the officially reported 5% growth rate, the highest proportion since 1997, according to government data.

Li designated boosting consumption as China’s top policy priority for 2025, saying that domestic demand is “sluggish." Officials also formally lowered their consumer inflation target to around 2%, the lowest level since 2003, a rare acknowledgment of the deflationary pressures brought about by weak spending at home.

Unlike in years past, when the call for more consumption was mostly limited to rhetoric, leaders are showing an increasing willingness to throw money at the problem. China raised its fiscal deficit target to 4% of gross domestic product for the first time in years, showing that the central government plans to step up borrowing to support the economy.

“Given the uncertainty right now we are seeing on the global stage, the domestic economy is becoming increasingly more important," said Tommy Xie, head of Greater China research and strategy at OCBC Bank in Singapore.

China has signaled backing for the private sector.

Still, certain stimulus measures announced for the year were more modest than some economists expected. Policymakers could be holding back some fire for later in the year if trade pressures indeed weigh on economic growth, Macquarie economists Larry Hu and Yuxiao Zhang told clients in a report Wednesday.

“The short-term concerns are at the fore, but that’s not to say industrial policy, the longer-term stuff, has been abandoned, but it’s not the priority at the moment," said Batson of Gavekal. “There’s a recognition that industrial-policy goals and the various long-term strategic objectives are going to come out better and be easier to achieve in the context of an economy that is broadly prosperous and growing at a decent rate."

A key part of the larger picture is unleashing China’s private sector, whose dynamism helped fuel the country’s decadeslong boom beginning in the 1980s, but which had been left in limbo in recent years after a string of industry crackdowns.

Last month, Chinese leader Xi Jinping gathered many of China’s leading entrepreneurs, including DeepSeek’s Liang Wenfeng and Alibaba co-founder Jack Ma, signaling government backing while also reminding them to uphold a “sense of national duty" as they develop their technology. A spokesman for China’s legislative body on Tuesday praised DeepSeek for showcasing China’s tech advances.

Now, when officials talk about boosting support for biomanufacturing, quantum technology, robotics, next-generation telecommunications and advanced manufacturing, as Li did Wednesday, fewer officials in Washington are likely to dismiss the competitive threat, after several years of widening restrictions aimed at curtailing Chinese capabilities.

Write to Jonathan Cheng at Jonathan.Cheng@wsj.com and Hannah Miao at hannah.miao@wsj.com.