President Trump on Friday again claimed that his response to the coronavirus was hindered by the Obama administration, which left office three years ago.

Mr. Trump attacked Mr. Obama, who served with Mr. Trump’s likely Democratic challenger, Vice President Joseph R. Biden Jr., in two posts on Twitter.

“For decades the @CDCgov looked at, and studied, its testing system, but did nothing about it,” Mr. Trump wrote. “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.

“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,” he continued. “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!” he wrote.