China issued a warning to the incoming Trump administration through its state-run media Friday that the U.S. risks a “large-scale war” if it follows through on Secretary of State nominee Rex Tillerson’s suggestion that the U.S. should block China’s access to its growing man-made islands in the South China Sea.

Two Chinese dailies, the saber-rattling Global Times and the English-language China Daily, took aggressive and at times condescending approaches to Tillerson’s stance on the issue during his Senate confirmation hearing on Wednesday. China Daily described the would-be secretary of state’s comments as a “mish-mash of naiveté, shortsightedness, worn-out prejudices, and unrealistic political fantasies.”

Tillerson, former CEO of Exxon Mobil, took a hard line toward China’s island-building and expansionist claims in the oft-disputed South China Sea, an international body of water and crucial trade route, and compared the country’s recent aggression there to “Russia’s taking of Crimea.”

China’s rapid island-building around the Spratly Islands — an archipelago that has long been a source of tension in the region — was a concern for the Obama administration, which responded by conducting regular “freedom of navigation” operations.

The most recent exercise, involving passing a United States Navy destroyer near the disputed islands, elicited an angry response from the Chinese Defense Ministry, which described it as “illegal” and “provocative.”

The mission stayed outside the internationally recognized 12-nautical-mile territorial limits of the disputed islands, but within waters China claims as its own. “This operation demonstrated that coastal states may not unlawfully restrict the navigation rights, freedoms, and lawful uses of the sea that the United States and all states are entitled to exercise under international law,” Josh Earnest, White House spokesman, said at the time.

James Mattis, Donald Trump’s pick for Secretary of Defense, reinforced such an approach, as is current U.S. policy, during his confirmation hearing Thursday.

“International waters are international waters, and we’ve got to figure out how we deal with holding onto the rules we’ve made over many years.” Mattis said, reiterating U.S. responsibilities in preserving freedom of navigation through the contested waters.

Malaysia, the Philippines, Taiwan, Vietnam, and Brunei all have territorial claims to the Spratly Islands, located along one of the world’s busiest trade routes.

“We’re going to have to send China a clear signal that, first, the island-building stops, and second, your access to those islands is not going to be allowed,” Tillerson said during his hearing.

The secretary of state nominee’s latter point clearly struck a nerve. “Tillerson had better bone up on nuclear power strategies if he wants to force a big nuclear power to withdraw from its own territories,” an unsigned Global Times editorial threatened.

Tillerson’s remarks would be a notable shift from current policy, one that experts told the Guardian would require a dramatic show of military force that could lead to “a crisis, a military clash.”

China’s official response was far more tame, but it revealed a key underlying assumption of territorial control over the disputed islands that will likely be a sticking point in future diplomatic discussions. China’s foreign ministry spokesman Lu Kang said China had the right to “conduct any kind of normal activities” in its territory and deflected from specifically addressing Tillerson’s comments on the U.S. preventing China from accessing the islands.

Tillerson is the latest official in Trump’s incoming administration to stake out a hard line on China. Trump’s incoming trade representative Robert Lighthizer and leader of the newly formed national trade council Peter Navarro are longtime critics of China and what they see as its regular abuse of free-trade agreements.