While Rex Tillerson's confirmation hearing as Trump's Secretary of State was for the most part uneventful, several hours into his back and forth with the Senate Foreign Relations Committee, Tillerson compared China’s actions to those of Russia in Crimea, saying a failure to respond had allowed it to “keep pushing the envelope” in the South China Sea. “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 also not going to be allowed” and that putting military assets on those islands was "akin to Russia’s taking Crimea” from Ukraine.

With that statement, America's likely next secretary of state "has set a course for a potentially serious confrontation with Beijing" according to Reuters, which added that his comments are "expected to enrage Beijing."

Tillerson, the former Exxon chairman and CEO, did not elaborate on what might be done to deny China access to the islands it has built up from South China Sea reefs, equipped with military-length airstrips and fortified with weapons. Trump's transition team did not immediately respond to a request for specifics on how China might be blocked from the artificial islands.

Tillerson said he considered China’s South China Sea activity "extremely worrisome" and that it would be a threat to the "entire global economy" if Beijing were able to dictate access to the waterway.

“This is the sort of off-the-cuff remark akin to a tweet that pours fuel on the fire and maybe makes things worse,” Malcolm Davis, a senior analyst at the Australian Strategic Policy Institute in Canberra told Bloomberg. “Short of going to war with China, there is nothing the Americans can do.”

He blamed the current situation on what he termed an inadequate U.S. response. "The failure of a response has allowed them just to keep pushing the envelope on this," Tillerson said.

China responded when its Foreign Ministry spokesman Lu Kand said China has been acting within the limits of its sovereignty. “Like the U.S., China has the right within its own territory to carry out normal activities,” he said at a regular briefing in Beijing. When asked repeatedly about Tillerson's comments on blocking access to islands, China's foreign ministry spokesman said he couldn't make any guesses as to what Tillerson was referring to and would not answer hypothetical questions, Reuters reported.

China's right to carry out 'normal activities' in its sovereign territory in the South China Sea is 'indisputable', Lu said, speaking at a daily briefing on Thursday. He did not elaborate.

Tillerson also said he would stand by U.S. defense treaties with Japan and South Korea. These had been in doubt after Trump said in an interview last March that he would consider withdrawing U.S. troops if allies didn’t pay more for their upkeep. Asked whether he agreed with Trump’s assertion that it wouldn’t be a bad thing for the U.S. if Japan and South Korea acquired nuclear weapons, Tillerson said he “did not agree."

"We have long-standing ally commitments with Japan and South Korea in the area and I think we would respond in accordance with those accords,” he said. “Certainly we have made commitments to Japan in terms of a guarantee of their defense.”

Pouring more gasoline on US-Sino relations, Tillerson called China's South China Sea island-building and declaration of an air defense zone in the East China Sea it contests with Japan "illegal actions." "They’re taking territory or control, or declaring control of territories that are not rightfully China’s."

Tillerson also said Washington needed to reaffirm its commitment to Taiwan, which Beijing regards as a renegade province, however he stopped short of Trump's questioning of Washington's long-standing policy on the issue. "I don’t know of any plans to alter the 'one China' position," Tillerson said.

Curiously, Tillerson's words went beyond Trump's own tough rhetoric on China. Regional military sources said while the U.S. navy had extensive capabilities in Asia to stage blocking operations with ships, submarines and planes, any such move against China's growing naval fleets would risk dangerous escalations.

Tillerson's criticism of China was not confined solely to geopolitics: he accused China of failing to live up to global agreements on trade and intellectual property, echoing past remarks by Trump, who has threatened to impose high, retaliatory tariffs on China.

But Tillerson also stressed the "deeply intertwined" nature of the world's two biggest economies. "We should not let disagreements over other issues exclude areas for productive partnership."