WHO Director-General Tedros Adhanom Ghebreyesus singled out President Donald Trump , whom he said he spoke with Tuesday, for doing a "great job" in leveraging public and private sector resources to fight the pandemic.

The World Health Organization praised the Trump administration's response to the COVID-19 outbreak, which has spread to all 50 states and infected at least 55,568 U.S. citizens.

"Fighting this pandemic needs political commitment and commitment at the highest level possible and the president's commitment, you have already seen it," Tedros said at a news briefing at the agency's headquarters in Geneva. "And that kind of leadership is very, very important, the whole of government approach, to mobilize all sectors to suppress the pandemic. So I know he's doing all he can."

Tedros said Trump was expanding testing and is putting in place other WHO recommendations. "He takes that seriously and that's what we see," Tedros said.

WHO officials said they also spoke Wednesday with Centers for Disease Control and Prevention Director Robert Redfield and National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci.

Dr. Mike Ryan, executive director of the WHO's health emergencies program, said he was "very impressed to see the work that their institutions and other institutions" are doing.

Ryan said the WHO has been working closely with the National Institutes of Health, which has been fast-tracking work with biotech company Moderna to develop a vaccine to prevent COVID-19. They began their first human trials on a potential vaccine last week.

"We rely heavily on the scientific innovation and public health prowess of the United States and very much appreciate the way in which Dr. Fauci broke down the issue yesterday when he spoke about the data," Ryan said. "And he spoke about getting down to the state and the county level and working through the problem and working through the issues."

The United States has the third-highest number of confirmed cases in the world, behind Italy and China, according to data compiled by John Hopkins University. More than half of the U.S. cases are in New York state, where local officials have tested more than 103,000 people and spent $1 billion fighting the pandemic.

Trump has imposed travel bans for much of Europe and Asia. The president's coronavirus task force is advising anyone who travels through New York to self-isolate for two weeks and monitor their symptoms if they leave the area.