Donald Trump is facing a backlash after appearing to mock Mitt Romney for self-isolating after spending time with fellow Republican senator Rand Paul, who tested positive for Covid-19.

The Utah senator is being extra cautious because his wife, Ann Romney, has multiple sclerosis.

The former presidential nominee released a statement on Sunday saying he has no symptoms but was getting tested for the virus, on the advice of his doctor.

On Sunday Mr Trump was asked in a White House briefing on Sunday about how Senate Republicans would win votes with several members in quarantine. After learning that Mr Romney was one of the members who took the advice to self-isolate, he said: "Romney's in isolation? Gee, that's too bad."

A reporter asked: "Do I detect sarcasm there?"

The president shook his head and responded: "None whatsoever."

Many were unconvinced because of recent disparaging comments about Mr Romney, the sole Republican to support removing the president from office on impeachment charges.

CNN analyst Asha Rangappa tweeted: "Imagine expressing glee - even veiled as saracsm - that someone might be infected with a life-threatening illness that could leave him unable to breathe and to possibly die...WHO DOES That?? Oh yeah, the president of the United States."

Mika Brzezinski, co-host of Morning Joe and herself a former target of slurs by Mr Trump, wrote: "The President behaves like a spoiled child .. comment about Romney ridiculous. I'm glad the reporter called him out and asked him about it.

PBS News Hour's White House Correspondent Yamiche Alcindor pointed out the apparent difference between Mr Trump's prepared and unprepared remarks, tweeting: "Classic example of President Trump.

"Trump speaking at the beginning of this press conference with prepared remarks: 'No American is alone as long as we're united.' A few minutes later, Trump, speaking without prepared remarks: "Romney's in isolation? Geeeeee - that's too bad."

The president's seemingly sarcastic response is just one of the many ways he has used the health crisis to denounce state representatives who criticise him or the federal government's inaction in January and February.

Governor JB Pritzker of Illinois complained on CNN's State of the Union about how federal inaction and a lack of supply had created the need for states to compete with each other for medical supplies, increasing prices.

"We're competing against each other, we're competing against other countries," Mr Pritzker said.

Mr Trump then tweeted: "Governor of Illinois, and a very small group of certain other Governors, together with Fake News CNN & Concast (MSDNC), shouldn't be blaming the Federal Government for their own shortcomings."

The president ignored reports from US intelligence agencies earlier this year that warned of the severity of Covid-19, according to the Washington Post – something he has denied. On Sunday, he announced that the National Guard would assist New York, California, and Washington, the states worst affected by Covid-19.

As of today, there are 35,000 reported cases and more than 500 deaths in the United States.