Japan says the US has apologised for a series of recent accidents on its territory involving American military equipment.
The incidents on the southern island of Okinawa included the emergency landings of two US military helicopters.
Okinawa Governor Takeshi Onaga said he was "lost for words" and wanted the US military to "feel ashamed" over the incidents.
The island hosts the largest US military presence in Japan.
Over the past few years, a number of accidents and crimes have led to growing local opposition to the US base.
Speaking to reporters, Japanese Defence Minister Itsunori Onodera confirmed he had received an apology from his American counterpart:
"The US Defence Secretary James Mattis told me about the details of the emergency landings of US aircraft and apologised for the situation where such incidents have been happening one after the other.
"Mr Mattis said the US fully understood the situation and would deal with it sincerely as a serious issue."
On Monday, a US attack helicopter made an emergency landing in the grounds of a hotel on the island.
The helicopter crew landed the aircraft because a warning light had come on, Japanese public broadcaster NHK reports.
On Saturday, another US military helicopter made an emergency landing on an Okinawan beach because of a faulty rotor.
No-one was injured in either incident.
The US presence on Okinawa in southern Japan is a key part of the post-war security alliance between the two countries. The base houses some 26,000 US troops.
In 2016, the murder of a woman was linked to an ex-Marine employed at one of the bases, which led to a temporary ban on alcohol as well as a midnight curfew.
The US government wants to move Futenma, the largest Marine base in Okinawa, to a more remote location on the island.
But Mr Onaga is leading a campaign to get the US military base off the island completely.
Incidents in recent months
- On Monday, a US military helicopter made an emergency landing in the grounds of a hotel after a warning light came on
- On Saturday, another US military helicopter made an emergency landing on an Okinawan beach because of a faulty rotor
- Last month, a window from a US military helicopter fell into a school sports ground near the Futenma marine air base in Okinawa; no-one was injured
- In November, a US serviceman caused a deadly car crash on the island. When the accident was linked to drink-driving, the US military banned all soldiers stationed in Japan from drinking alcohol
- In October, an American military helicopter burst into flames after landing in an empty field on the island