"They have got some problems. That’s not good because when bad folks have problems, they do bad things," Biden said at a political fundraiser in Utah.
Biden's remarks were reminiscent of comments he made at another fundraiser in June when he referred to President Xi Jinping as a "dictator." China called the remarks a provocation.
Those comments came shortly after U.S. Secretary of State Antony Blinken completed a visit to China aimed at stabilizing relations that Beijing described as being at their lowest point since formal ties were established in 1979.
China's consumer sector fell into deflation and factory-gate prices extended declines in July. China may be entering an era of much slower economic growth with stagnated consumer prices and wages, contrasting with inflation elsewhere in the world.
The United States, the world's largest economy, has fought high inflation and seen a robust labor market.
"China is in trouble," Biden said on Thursday. He said he did not want to hurt China and wanted a rational relationship with the country.
Biden on Wednesday signed an executive order that will prohibit some new U.S. investment in China in sensitive technologies like computer chips. China, which has the world's second largest economy, said it was "gravely concerned" about the order and reserved the right to take measures.