Lt Gov Ray Tenorio said at a news conference with the president of the Guam Visitors Bureau in Tokyo that Guam remains in a "state of normalcy."
Japan is a major source of tourists for the Pacific island, with a tourism relationship that has lasted for more than 50 years.
North Korea threatened recently to launch ballistic missiles into waters near Guam. However, leader Kim Jong Un said later that he would watch Washington's conduct before executing the plan.
The US and South Korea began an annual military drill Monday. North Korea typically responds to such exercises with weapons tests, though it is unclear if that would include sending missiles in Guam's direction.
The joint training, which follows North Korea's two intercontinental ballistic missile tests last month, is scheduled to last for 11 days.
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