President Donald Trump said on Friday that he was being sarcastic when he raised the possibility of using disinfectant inside people's bodies to fight the coronavirus, seeking to walk back comments that alarmed medical professionals worldwide.

Trump said at a Thursday news briefing that scientists should explore whether inserting light or disinfectant into the bodies of coronavirus patients might help treat COVID-19, the respiratory illness caused by the virus.

At an Oval Office event on Friday, Trump sought to walk back those comments while also seeming to continue to advance his theory that disinfectants and sunlight might ultimately help within the body.

"I was asking a question sarcastically to reporters like you just to see what would happen," he told journalists at an event in the Oval Office.

His remarks on Thursday, directed at Dr. Deborah Birx, who is coordinating the president's coronavirus task force, and William Bryan, acting head of the U.S. Department of Homeland Security's Science and Technology Directorate, did not come across as sarcastic.

Pressed repeatedly about the issue on Friday, Trump said he was not encouraging people to ingest disinfectant.

The Maryland Emergency Management Agency said it had received several calls about disinfectant use and COVID-19. "This is a reminder that under no circumstances should any disinfectant product be administered into the body through injection, ingestion or any other route," it said in a tweet.

Health professionals have been encouraging people for some time to wash their hands thoroughly with soap or to use hand sanitizer to help stop the spread of the virus.

At the Thursday briefing, Bryan unveiled findings that the coronavirus appears to weaken more quickly when exposed to sunlight, heat and humidity. That message stuck with Trump, who, while conceding that he is not a doctor, has used his metaphorical megaphone as president to talk up treatments and put a positive spin on his administration's handling of the outbreak.

"I do think that disinfectant on the hands could have a very good effect," he said on Friday, continuing with the theme.

"Sun and heat, and humidity wipe it out. And this is from tests - they've been doing these tests for ... a number of months. And the result - so then I said, ‘Well, how do we do it inside the body or even outside the body with the hands and disinfectant I think would work.'"

Trump's initial comments about the issue raised concerns that anxious people might poison themselves while trying to fight the virus, prompting an international chorus of doctors and health experts to urge people not to drink or inject disinfectant.