A previous poll, conducted from April 15 to 20, indicated that 36 percent of Americans approved of Trump's performance, Xinhua reported.
The decline is largely attributed to growing public dissatisfaction with his handling of cost-of-living issues, with approval dropping to 22 percent from 25 percent in the prior poll.
The US and Israeli war of aggression against Iran, launched on February 28, has driven gasoline prices in the United States up by more than 40 percent.
The survey also found that only 34 percent of Americans support the US war on Iran, down from 36 percent in mid-April and 38 percent in mid-March.
The nationwide online poll collected responses from 1,269 US adults