House Speaker Nancy Pelosi has labelled President Donald Trump a "weak leader" over his coronavirus response, after the president released a series of tweets against the Democrat.

She criticised the president for ignoring scientific facts when considering reopening the US when appearing on Fox News Sunday to speak about the current state of the country.

"Leaders - leaders take responsibility. So I said he's a weak leader. He doesn't take responsibility. He places blame - blame on others," Ms Pelosi said. "And that might have been OK before, but we cannot continue down a path that is, again I'll come back to science, science, science, evidence, data on how we should go forward."

The president pushed forward his three-phase plan this week that would guide states on how they would reopen amid the pandemic.

At the same time, Mr Trump has sparked criticism for encouraging states to be "liberated" even though they have yet to reach all the criteria he put in place to allow them to move to phase one.

Fox News host Chris Wallace asked the speaker how she could criticise the president over his new plan after it received a stamp of approval from infectious disease expert Dr Anthony Fauci. Ms Pelosi said the failure in testing on a federal level makes the plan hard to achieve.

"But we're way late on it and that is a failure. The president gets an F, a failure on the testing," she said. "Dr. Fauci's right. If it is done properly, it hasn't been and I think when he puts in the 'if it's done' is an admission that it hasn't been done."

Ms Pelosi also ABC's This Week on Sunday morning and was asked about the president's negative tweets against her this past week.

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He called her a "weak person", "poor leader", and "incompetent" for her own response to the coronavirus pandemic. The president also accused the speaker of being "away on vacation" instead of passing more funding for the Paycheck Protection Program (PPP).

"Frankly, I don't pay that much attention to the president's tweets against me," Ms Pelosi said. "As I've said, he's a poor leader. He's always trying to avoid responsibility and assign blame."

"I'm afraid that he's going to act on the set basis of what he's acted before," she added about his response. "It's a hoax. It's magically going to disappear."

Democrats have held back on passing the PPP this week in a bid to get funding to state and local governments as well as small businesses. But the Trump administration, and Republicans, have pushed back from giving any more funding to states.