China hit out at the "dark history" of the US intelligence community Thursday, after President Joe Biden ordered a probe into the Covid-19 origins which threatens to set the course for relations between world's top economies.
Washington is reviewing its diplomatic position with China on issues spanning trade, technological supremacy and rights, while it steps up efforts to hook Western democracies into a united diplomatic front against perceived Chinese aggression.
The countries' trade envoys have held "candid" phone talks on the progress of a deal plotted as a pathway out of a trade war sparked by former President Donald Trump, which saw tariffs lumped on tens of billions of dollars of the rivals' goods.
But on Wednesday, President Biden reopened a barely healed sore between the countries by ordering US intelligence agencies to report to him within 90 days on whether the Covid-19 virus first emerged in China from an animal source or from a laboratory accident.
The lab-leak theory, initially trotted out by Trump then dismissed as "highly unlikely" by a delayed World Health Organization mission to China, has resurfaced in recent days, driven by Washington.
China is intensely sensitive to allegations it could have done more to stop the spread of a pandemic that has gone on to kill well over 3.4 million people and has eviscerated economies since emerging in the central Chinese city of Wuhan in late 2019.
Beijing rejects the theory the virus may have emerged from a virology lab in Wuhan and has instead accused the US of peddling "conspiracies" and politicising the pandemic.
The Biden administration's "motive and purposes are clear", Zhao Lijian a ministry of foreign affairs spokesman said on Thursday, rejecting the need for a new investigation into the pandemic.
"The dark history of the US intelligence community has long been known to the world," he added, referring to the US' unfounded allegations of weapons of mass destruction which led to its invasion of Iraq.
Reviving the lab leak theory "is disrespectful to science... and also a disruption to the global fight against the pandemic", Zhao said.
But the idea of virus release from a Wuhan lab is gaining increasing traction in the United States.
Citing a US intelligence report, The Wall Street Journal reported Sunday that a trio from the Wuhan Institute of Virology were hospitalised with a seasonal illness in November 2019, a month before Beijing disclosed the existence of a mysterious pneumonia outbreak.
The natural origin hypothesis -- backed as the most likely by the WHO expert team who visited China -- holds that the virus emerged in bats then passed to humans, likely via an intermediary species.
This theory was widely accepted at the start of the pandemic, but as time has worn on, scientists have not found a virus in either bats or another animal that matches the genetic signature of SARS-CoV-2.
- Trade talks -
China is at pains to move on from the pandemic origin quest, driven by Western nations including Australia and the UK.
Instead it is focused on its economic rebound since squashing the pandemic inside its borders.
The commerce ministry on Thursday welcomed trade talks with Washington which are part of a deal to end the bruising trade war.
The two countries signed the so-called "phase 1" agreement in January 2020, in which Beijing pledged to increase its purchases of American products and services by at least $200 billion over 2020 and 2021.
But top US trade negotiator Katherine Tai has said she is analysing whether the terms of that pact have been met by China, with some experts saying Beijing is falling up to 40 percent short on its agreement to buy US goods.
The talks were the first between top trade envoys since Biden came to office and are significant given previous high-level contacts -- including a face-to-face meeting of foreign envoys in Alaska -- have collapsed in acrimony.
But the trade discussions are a matter of "diplomatic protocol more than about re-engagement" says Alex Capri, Research Fellow, Hinrich Foundation.
Despite Biden's less hawkish language, the US-China relationship appears on the "same trajectory as his predecessor", says Capri of "systemic rivalry, defined by techno-nationalist and neo-mercantilist competition."