NEW YORK -- U.S. President Donald Trump doubled down on his criticism of the World Health Organization on Friday, suggesting that it wrongly dismissed a year-end alert from Taiwan over the new coronavirus.

"Why did the W.H.O. Ignore an email from Taiwanese health officials in late December alerting them to the possibility that CoronaVirus could be transmitted between humans?" Trump tweeted Friday. "Why did the W.H.O. make several claims about the CoronaVirus that [are] either inaccurate or misleading in January and February, as the Virus spread globally? Why did the W.H.O. wait as long as it did to take decisive action?" he asked, quoting a think tank scholar.

Trump's renewed attacks came the day after he slammed the WHO's handling of the outbreak in a Group of Seven video meeting he convened and chaired.

The White House said that "much of the conversation" during the videoconference "centered on the lack of transparency and chronic mismanagement of the pandemic by the WHO" and that the leaders "called for a thorough review and reform process."

The statement did not mention that Trump was rebutted by German Chancellor Angela Merkel, who expressed full support for the WHO and stressed that "the pandemic can only be overcome with a strong and coordinated international response."

Trump's mention of the Taiwanese email looks to be part of a new strategy to attack the close relationship between the WHO and China. Taiwan has long been barred from WHO membership over objections from China, which considers the island a province rather than a stand-alone entity.

And this strategy appears closely linked to the emergence of former Vice President Joe Biden as his presumptive Democratic opponent in this year's presidential election.

U.S. Vice President Joe Biden and his son Hunter Biden seen attending an NCAA basketball game in Washington in 2010. © Reuters

Biden's relationship with China "will absolutely be a big issue in the campaign," Trump 2020 communications director Tim Murtaugh told political news outlet The Hill on Thursday.

The Trump campaign has focused on son Hunter Biden's board seat at Chinese private equity firm BHR Partners. It will seek to expose the Biden family's "financial intertwining with China" and "Hunter Biden's dependence on China for income -- lots and lots of income," Murtaugh said. Hunter Biden's attorney has described the position as unpaid.

"Everyone should be aware of Joe Biden's history of being too cozy with China and going soft on China and it really begins with saying that they are not an economic threat ... which is either willfully ignorant or just inept," Murtaugh said.

Meanwhile, criticism of the WHO is mounting on Capitol Hill. China hawk Marco Rubio and seven other Republican senators this week urged Trump to "pursue an open and transparent investigation into the origins of COVID-19, as well as the WHO's decision-making related to the crisis."

"We commend you for taking steps to investigate China's influence within international bodies such as the WHO," they wrote in a letter to the Republican president.

The probe should include "any pressure it received from Beijing to downplay the apparent spread of the virus and its treatment of Taiwan, a strong democratic partner of the United States," the letter said.

Chinese Foreign Ministry spokesman Zhao Lijian dismissed such criticism as "totally smear and rumor-mongering against China" in a press conference Friday.

"As the most authoritative and professional international organization in the field of global public health security, WHO has actively fulfilled its duties with objective, science-based and fair position, and played an important coordinating and leading role in assisting countries respond to the outbreak and boost international cooperation on COVID-19," Zhao said.

"I would like to stress that the international community should work together to fight the epidemic," he said. "We hope all parties of the international community can take concrete actions to uphold multilateralism, strengthen and improve the global governance system with the U.N. as the core," as well as "support WHO's leading role in global anti-pandemic cooperation."

The WHO told Reuters last week that the Taiwanese email "makes no mention of human-to-human transmission." But the Taiwan Centers for Disease Control said the wording did imply a "real possibility" of it.

Additional reporting by Alex Fang in New York.