A senior Chinese diplomat accused the U.S. Army of spreading the coronavirus to China hours after his colleagues complained that efforts to assign blame distract from efforts to counter the pandemic.

“When did patient zero begin in US?” Chinese Foreign Ministry spokesman Lijian Zhao tweeted Thursday. “It might be US army who brought the epidemic to Wuhan.”

Chinese officials have been casting doubt on the origins of the virus in recent weeks, even though the outbreak first surfaced in Wuhan city in Hubei province. The Communist Party’s initial attempts to hide the outbreak outraged many Chinese citizens, who blamed the regime for the crisis, but Chinese officials have denounced President Trump’s administration for making similar observations.

“Every minute wasted on smearing and complaining would be better spent on enhancing domestic response and international cooperation,” another Chinese Foreign Ministry spokesman, Geng Shuang, said on Thursday, hours before his colleague’s targeting of the U.S. Army.

Western governments lost precious time to prepare for the pandemic because Chinese officials “covered up” the outbreak when it first appeared, a senior White House official charged on Wednesday.

“It probably cost the world community two months,” White House national security adviser Robert O’Brien said at an event in Washington. “I think we could have dramatically curtailed what happened both in China and what's now happening across the world.”

That comment angered Chinese diplomats, who have been touting their imposition of mass quarantines in Hubei province as a sign of the usefulness of the communist political system since last month.

“It is China's forceful measures and Chinese people's huge sacrifice that stemmed the outward spread of COVID-19, thus buying valuable time for the world to respond,” Geng said Thursday.

Chinese officials announced this week that all visitors to Beijing must spend 14 days in quarantine after weeks of denouncing the United States for adopting travel restrictions and criticizing Trump for evacuating American citizens from Hubei. Those decisions, the Chinese Foreign Ministry claimed, were “creating and spreading panic.”

Party leaders also decided this month to evacuate Chinese citizens from Iran, which has encouraged travel between Tehran and China in recent months and now faces one of the worst coronavirus outbreaks in the world.

“Faced with the pandemic, the guiding consensus for all countries is to join hands and overcome difficulties together,” Geng said Thursday. “Pointing the finger at others is certainly not constructive, nor will it get any backing.”