WASHINGTON--China cut off contacts with the United States on vital issues Friday--including military matters and crucial climate cooperation --as concerns rose that the Communist government's hostile reaction to House Speaker Nancy Pelosi's Taiwan visit could signal a lasting, more aggressive approach toward its U.S. rival and the self-ruled island.

China's move to freeze key lines of communication compounded the worsening of relations from Pelosi’s visit and from the Chinese response with military exercises off Taiwan, including firing missiles that splashed down in surrounding waters.

After the White House summoned China's ambassador, Qin Gang, late Thursday to protest the military exercises, White House spokesman John Kirby on Friday condemned the decision to end important dialogue with the United States as “irresponsible.”

The White House spokesman blasted China's “provocative” actions since Pelosi's trip to Taiwan, which China claims as part of its territory. But Kirby noted that some channels of communication remain open between military officials in the two countries. He repeated daily assurances that the U.S. had not changed its policy toward the Communist mainland and the self-ruled island.

“Bottom line is we’re going to continue our efforts to keep opening lines of communication that are protecting our interests and our values,” Kirby said. He declined to speak about any damage to long-term relations between China and the United States, calling that a discussion for later.

Taiwan has put its military on alert and staged civil defense drills, but the overall mood remained calm on Friday. Flights have been canceled or diverted and fishermen have remained in port to avoid the Chinese drills.

On the Chinese coast across from Taiwan, tourists gathered to try to catch a glimpse of military aircraft.

A minister at the Chinese Embassy in Washington, Jing Quan, told reporters that Pelosi's mission of support for the democratic government of Taiwan has had "a severe impact on the political foundation of China-U.S. relations, seriously infringed upon China’s sovereignty and (territorial) integrity and ... undermines peace and stability across the Taiwan Straits.”

Long term, a significantly more confrontational relationship between China and the U.S. threatens an equilibrium under which Presidents Joe Biden and Xi Jinping's governments have sparred on human rights, trade, competition and countless other issues but avoided direct conflict and maintained occasional top-level contacts toward other matters, including cutting climate-damaging emissions.

A joint U.S.-China deal to fight climate change struck by Xi and then-President Barack Obama in November of 2014 is credited as a turning point that led to the landmark 2015 Paris agreement in which nearly every nation in the world pledged to try to curb emissions of heat-trapping gases. Seven years later during climate talks in Glasgow, another U.S.-China deal helped smooth over bumps to another international climate deal.

China and the United States are the world’s No. 1 and No. 2 climate polluters, together producing nearly 40% of all fossil-fuel emissions.

Ominously, experts in China-U.S. relations warned that China's diplomatic and military moves appeared to go beyond retaliatory measures for the visit and could open a new, more openly hostile era, and a more uncertain time for Taiwan's democratic government.

China-U.S. relations are “in a downward spiral," said Bonnie Glaser, head of the Asia program at the German Marshall Fund.

“And I think that China is likely to change the status quo in the Taiwan Strait in ways that are going to be harmful to Taiwan and are going to be disadvantageous to the United States," Glaser said.

In recent years, other rounds of tensions between China and its neighbors over the India border, regional islands and the South China Sea have ended with China asserting new territorial claims and enforcing them, noted John Culver, a former East Asia national intelligence officer, now a senior fellow at the Atlantic Council. The same could happen now over Taiwan, Culver said. “So I don't know how this ends. We've seen how it begins.”

China's measures this week are the latest steps intended to punish the U.S. for allowing the visit to the island it claims as its own territory, to be annexed by force if necessary. China on Thursday launched threatening military exercises just off Taiwan's coasts, running through Sunday.

Some missiles were sent flying over Taiwan itself, Chinese officials told state media — a significant increase in China's menacing of the island.

China routinely complains when Taiwan has direct contacts with foreign governments, but its response to the Pelosi visit — she was the highest-ranking American official in 25 years —has been unusually strong.

It appears to derail a rare encouraging note — high-level in-person meetings between top officials in recent months including the defense chiefs at an Asia security conference in Singapore and Foreign Minister Wang Yi and Secretary of State Antony Blinken at a Group of 20 meeting in Indonesia.

Those talks were viewed as steps in a positive direction in an otherwise poisoned relationship. Now, talks have been suspended even on climate, where the two countries’ envoys had met multiple times.

China stopped short of interrupting economic and trade talks, where it is looking to Biden to lift tariffs imposed by President Donald Trump on imports from China.

On Friday, China's Foreign Ministry said dialogue between U.S. and Chinese regional commanders and defense department heads would be canceled, along with talks on military maritime safety. Cooperation on returning illegal immigrants, criminal investigations, transnational crime, illegal drugs and climate change will be suspended, the ministry said.

China's actions come ahead of a key congress of the ruling Communist Party later this year at which President Xi is expected to obtain a third five-year term as party leader. With the economy stumbling, the party has stoked nationalism and issued near-daily attacks on the government of Taiwanese President Tsai Ing-wen, which refuses to recognize Taiwan as part of China.

China said Friday that more than 100 warplanes and 10 warships have taken part in live-fire military drills surrounding Taiwan over the past two days. Also, mainly symbolic sanctions against Pelosi and her family were announced.

On the China coast, fighter jets could be heard flying overhead, and tourists taking photos chanted, “Let’s take Taiwan back," looking out into the blue waters of the Taiwan Strait from Pingtan island, a popular scenic spot in China's Fujian province.

Pelosi's visit has stirred emotions among the Chinese public, and the government's response “makes us feel our motherland is very powerful and gives us confidence that the return of Taiwan is the irresistible trend,” said Wang Lu, a tourist from neighboring Zhejiang province.

China is a “powerful country and it will not allow anyone to offend its own territory,” said Liu Bolin, a high school student visiting the island.

China's insistence that Taiwan is its territory and its threat to use force to reclaim control have featured in Communist Party statements, the education system and the state-controlled media for more than seven decades since the sides were divided amid civil war in 1949.

Taiwan residents overwhelmingly favor maintaining the status quo of de facto independence and reject China's demands that the island unify with the mainland under Communist control.

Beyond Taiwan, five of the missiles fired by China landed in Japan’s Exclusive Economic Zone off Hateruma, an island far south of Japan’s main islands, Japanese Defense Minister Nobuo Kishi said. He said Japan protested the missiles to China as “serious threats to Japan’s national security and the safety of the Japanese people.”

In Tokyo, where Pelosi is winding up her Asia trip, she said China cannot stop U.S. officials from visiting Taiwan.