The U.S. issued a formal diplomatic complaint known as a démarche over the Russian government’s response to the reported death of a lab worker from an anti-plague institute in Siberia, urging the country to increase transparency surrounding the incident, ABC News has learned.

“We have officially requested additional information from the Russian government. We are also in official communication with other countries around the world to share information,” a State Department spokesperson said.

A U.S. official said early Wednesday that the démarche was transmitted to representatives of the Russian government within the last few hours. The démarche itself is classified, but the official said it reminds Moscow of its requirements to comply with international health regulations.

The action came ahead of what President Donald Trump said was a scheduled call between him and his Russian counterpart, Vladimir Putin. Trump on Tuesday told reporters at the White House that the call had been scheduled and would happen “very soon,” adding that it would be “probably tomorrow.”

Trump said their conversation was expected to touch on the heightened scrutiny of Russia’s response after some Russian media and public figures reported a death potentially connected to the Irkutsk Anti-Plague Institute.

Russian authorities have said only that that the case of the lab worker’s reported death was “pneumonia of an unknown cause,” with the health agency Rospotrebnadzor saying tests showed no link with her work. They issued a statement saying that “no accidents have been detected at the Irkutsk Anti-Plague Institute while working with pathogenic microorganisms.”

Rospotrebnadzor’s office for the Irkutsk region issued on Tuesday a statement, saying, “A false message is being circulated online about the introduction of an enhanced sanitary and epidemiological regime and strict restrictions in the Irkutsk region.”

The U.S. Embassy in Moscow said in a Tuesday health alert that it was aware of the press reports, saying, “We continue to track the situation closely.” The State Department reminded Americans not to travel to Russia, saying the U.S. government has limited ability to help its citizens who go there. Additional restrictions may be in place for some regions, the embassy said.

Presidential press secretary Dmitry Peskov told reporters on Wednesday that official information would come directly from Rospotrebnadzor, adding, “the media are reporting a great deal right now, and the overwhelming majority of what the media are reporting around this situation is false information.”

As Russian officials came under scrutiny, U.S. officials offered to provide assistance. Trump said the U.S. was willing to help Russia after the U.S. State Department announced it was monitoring the reportedly fatal case of “pneumonia of an unknown etiology.”

“Anybody that has that kind of a problem, we’re always willing to help,” Trump told reporters Monday.

Asked about how the U.S. is planning to mitigate the risk coming from Russia, Trump said that his administration is “looking at it very strongly.”

Russia said it would welcome help from the United States, but also sought to downplay concern.

“It is always very good when mutual assistance is offered,” Peskov told journalists on Monday. Peskov then appeared to downplay Trump’s suggestion the issue was a “major problem for Russia,” telling a journalist he had not heard that framing.

“To be honest, I did not hear the president’s words that he considers this a major problem for Russia,” Peskov said. “As far as I remember it was not said that way, although I may be mistaken.”

Secretary of State Marco Rubio, asked Tuesday in Iceland by ABC News whether he had reason to believe there has been an accidental release of an intentionally modified strain of the plague, said it would “irresponsible for me here to sit and speculate because we just don’t have all the information yet.”

“I think it’s incumbent upon Russia to obviously share more information with the world. That’s what they should do,” the secretary said.

Rubio said his department was tracking the situation “hour by hour.”

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