US inflation rose 0.4% in May, mainly driven by a sharp increase in petrol prices, the US Department of Labor has said.
The 10.4% petrol price increase in May was the biggest since June 2009.
Core inflation, which strips out food and energy prices, rose 0.1% in the month,according to official figures.
Food prices were unchanged for a second month running, but may rise in the coming months after a shortage of eggs in some parts of the country.
Over the past 12 months, overall inflation has shown no increase, while core inflation is up 1.7%, both showing modest inflation pressures