US State Department spokeswoman Jennifer Psaki reiterated a travel warning issued a day earlier by the agency, which noted that in the past 18 months North Korea had detained several American citizens who were part of organised tours, Xinhua reported.
"US citizens should not assume that joining a group tour or using a tour guide will protect them from being detained or arrested by North Korean authorities," she told reporters at a daily news briefing.
"We strongly recommend against all travel by United States citizens to North Korea," she added.
The US has no diplomatic relations with North Korea. The embassy of Sweden is acting as Washington's protecting power in the country.