Donald Trump said on Friday morning that coronavirus testing in the United States will soon happen on a large scale, but without giving details, as he lashed out at the federal public health agency and former president Barack Obama over the chaos.

Meanwhile one of his top health officials, Anthony Fauci, warned on breakfast TV that the US was at a “critical point” in its response to the spread of the virus and that cases had not yet peaked. Fauci told the US Congress on Thursday that the system for testing for Covid-19 in the US was not geared up for requirements and that that was “a failing”.

On Friday, referring to the federal Centers for Disease Control and Prevention (CDC), the president tweeted: “For decades the @CDCgov looked at, and studied, its testing system, but did nothing about it. It would always be inadequate and slow for a large scale pandemic, but a pandemic would never happen, they hoped. President Obama made changes that only complicated things further.”

He went on: “Their response to H1N1 Swine Flu was a full scale disaster, with thousands dying, and nothing meaningful done to fix the testing problem, until now. The changes have been made and testing will soon happen on a very large scale basis. All Red Tape has been cut, ready to go!” Swine flu became a pandemic around a decade ago.

Trump also criticized the Centers for Disease Control and Prevention, one of the US organizations leading the fight against the deadly infection, for having a testing system that he said would “always be inadequate and slow for a large scale pandemic”.

Trump did not elaborate on why the CDC system, one of the US organizations leading the fight against the deadly infection, was inadequate, but Fauci had earlier said people cannot get tests easily.

Fauci, the head of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said: “US officials and lawmakers are struggling to get a sense of how many people in the country have contracted the virus, which they attribute to low testing rates.”

On ABC’s Good Morning America (GMA) breakfast news show he warned that there was worse to come for the US as coronavirus spreads. It has now reached 46 US states and the death toll is at least 40.

“It’s clearly going to get worse before it gets better,” he told GMA. “If you look at the pattern of viruses, like what was going on in China and Italy and South Korea, you have a big spike and after much suffering and death it goes back down again.”

He said the United States was currently at a critical point in its response.

“There is no doubt that we have not peaked yet,” he said.

He said he hoped the US would not have to shut down as a country in the way that others such as China and lately Italy have, saying, “I’m not sure it will get to that, but we have to respond over the days and weeks.”

He sought to reassure that “broad, blanket testing” was on its way for those needing tests in the US and he hoped that the kind of shut downs of gatherings, cities and states declaring emergencies, with mass quarantining and maximum working from home would not last too long.

Fauci said it would last “several weeks”, maybe “up to eight weeks or more, I hope two, three, four weeks”.