On Wednesday, President Trump said "talking is not the answer" with the state that has refused to dial back its ballistic missile tests despite United Nations economic sanctions.
The ban includes exceptions for journalists and humanitarian workers and will last one year unless the administration extends it.
Tour operators said it's a "real shame" the ban will prevent Americans engaging with ordinary North Korean citizens.
Koryo Tours General Manager Simon Cockerell said its led to a decrease in bookings as US tourists make up around 20 per cent of western visitors.
Heidi Linton, director of the US-based charity Christian Friends of Korea, said she wasn't sure how long it could take for travel approval to come through.
The organisation, which fights tuberculosis and hepatitis, has been working in North Korea for more than 20 years.
"The devil is always in the detail," she told AP after landing in Beijing. "These trips take a long time to plan and organise and so, if travel approval doesn't come in a timely way, it's a de facto denial."
Linton said the organisation appreciated the US government's concern for its people, but said there was a "tremendous need" for humanitarian work in North Korea.
"I think it's very important that there be opportunities for people to understand one another in person," Linton said.
It comes as US bombers and jet fighters took part in a live fire drill in South Korea following North Korea's missile launch over Japan which has raised fears of a miscalculation on the Peninsula.
"South Korean and US air forces conducted an air interdiction exercise in order to strongly cope with North Korea's repeated firing of ballistic missiles and development of nuclear weapons," the South's air force said in a statement.
The test involved two B-1B "Lancer" bombers from Guam and four F-35B stealth jet fighters from the Marine Corps' Iwakuni air base in Japan, with four South Korean jet fighters also taking part.
US flights from Guam infuriate North Korea, which cited them when announcing plans to fire towards Guam.
It was one of the moves that saw tensions spiral this month, along with a new set of UN Security Council sanctions, US President Donald Trump's apocalyptic warning to rain "fire and fury" on Pyongyang, and culminating with the North firing a missile over Japan on Tuesday.
The UK and Australia have called on China to enforce further sanctions against North Korea, saying it has the greatest leverage.
Foreign ministry spokeswoman Hua Chunying said sanctions alone "cannot fundamentally resolve the issue", amid reports the three countries were pushing for new restrictions on North Korean oil imports and foreign workers.
"The current situation on the Korean peninsula is not a screenplay, it's not a computer game. It is a real situation that directly bears on the security of the people on the peninsula and the whole regional peace and tranquillity," she said.
