World Health Organization officials on Wednesday mounted a defense of their response to the new and worrisome Ebola outbreak centered in the Democratic Republic of the Congo, after U.S. Secretary of State Marco Rubio said the agency was “a little late” in identifying infections.

WHO authorities stressed that their role is to offer technical and operational help to national health agencies, which have primary responsibility for detecting the spread of diseases under international rules.

“We don’t replace the country’s work,” Tedros Adhanom Ghebreyesus, WHO’s director-general, said at a press briefing. “We only support them.”

Tedros said Rubio’s remarks “could be from lack of understanding of how IHR works, and the responsibilities of WHO and other entities,” referring to the International Health Regulations, which set out countries’ obligations during health emergencies.

Rubio’s comments on Tuesday were just the latest criticism from the Trump administration and its allies of the global health agency. President Trump has also pulled the U.S. out of the WHO, forcing it to make major budget cuts. The administration has also drastically reduced U.S. support for global health initiatives, including in the DRC, which insiders say could have hampered the detection of the outbreak.