• Relations between US and China are at their worst since the normalisation of relations in the late 1970s
• Tensions sparked by Pelosi visit expected to intensify, but G20 and Apec summits in November offer chance for a reset, observers note

US-China relations are at their lowest point in half a century but worse may be in store before a reset seems possible, diplomatic observers said.

This comes as tensions continue to escalate over US House Speaker Nancy Pelosi's visit to Taiwan, which Beijing sees as a violation of its sovereignty, with neither side wanting to be seen as backing down.

Beijing, which repeatedly warned against the visit, has responded with severe condemnation and days of live-fire drills around Taiwan, including dozens of incursions over the median line in the Taiwan Strait, a de facto boundary that it had hitherto honoured.

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Washington, meanwhile, has pledged to continue Taiwan Strait transits and freedom of navigation operations in the region, where it has prolonged the deployment of its USS Ronald Reagan carrier strike group.

"When we said China-US relations had reached rock bottom during the [Donald] Trump administration, we really misread it," Lu Xiang, a specialist on US-China relations at the Chinese Academy of Social Sciences (CASS), said.

"The Pelosi incident is very damaging. China's reaction will also continue. If there are further moves there will be further countermeasures."

US policies towards China under former president Donald Trump included a slew of tariffs on Chinese imports and sanctions on Chinese officials for alleged human rights violations in Xinjiang and Hong Kong.

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But relations have become more "chaotic" since Joe Biden took office, with Pelosi's visit coming days after a phone call between the US and Chinese presidents, Lu said.

In the highly anticipated two-hour phone call on July 28, President Xi Jinping had warned Washington against "playing with fire". Pelosi, who set off on an official four-nation Asian trip on July 31, landed in Taipei for an unannounced visit on August 2.

"Relations between the two countries are at their worst since the normalisation of relations [in the late 1970s]," Lu said.