"It is deeply frustrating that North Korea continues to show such disregard for UN Security Council resolutions, which prohibit all such missile launches".
Japan's government says it counted four missiles landing in the Sea of Japan, the body of water between Korea and Japan.
There was a "low chance" the projectiles were intercontinental ballistic missiles, he said. Another U.S. defense official who spoke on the condition of anonymity said the missiles splashed down about 200 miles off Japan's coast and at least one of the missiles was detected and tracked by the USS Curtis Wilbur, a guided-missile destroyer, which was nearby.
Monday's launch came ahead of a trip to Japan, China and South Korea by new US Secretary of State Rex Tillerson this month, pointed out Dongguk University professor Kim Yong-Hyun.
In Gardner's view, the missile launch is especially worrisome given assertions by North Korea that it has developed a weapon capable of reaching American soil.
The United Nations on Monday deplored North Korea´s latest ballistic missile launches and urged Pyongyang to refrain from further provocations.
In addition to the Carl Vinson, the F-35 stealth fighter jets, the most advanced military aircraft, which were deployed for US forces stationed in Japan in January, are scheduled to take part in the drills for the first time.
North Korean dictator Kim Jong-un may have been rattled by the USA cyber effort.
Analysts told VICE News the tests could be meant to send a message that North Korea will respond to any pre-emptive measures which seek to hamper its development of an intercontinental ballistic missile (ICBM).
The initial test-firing it had been condemned by the UN, the United States, South Korea and Japan since Donald Trump became USA president. "If that's true, North Korea will not stop its programme, no matter the cost".
Pyongyang has test-launched a series of missiles of various ranges in recent months, including a new intermediate-range missile in February; it also conducted two nuclear tests a year ago. The large-scale field training drills called Foal Eagle started last Wednesday and the command post exercise Key Resolve will start next week. The messages informed the "21st exploration team" to review their "math assignment" which many believe is a coded message system for spies in South Korea.
Tensions have escalated in recent weeks between China and South Korea over United States plans to deploy a missile-defense system known as Terminal High Altitude Area Defense (THAAD) on the Korean Peninsula, part of measures to thwart Kim from gaining the ability to strike the continental USA with a nuclear warhead.
Pyongyang also is angry over the allies' plans to station an advanced U.S. Terminal High Altitude Area Defense missile system, known as THAAD, in the South.
China is anxious the system's radar may be used by the USA to spy on its military development. The U.S. insists it would be aimed only at North Korea. It also conducted two nuclear tests past year.
China's Defense Budget to Rise 7 Percent
China, the Philippines, Vietnam, Malaysia, Brunei, and Taiwan have claims in the region. USA activities, to a certain extent, are a barometer for the situation there.