(Reuters) - North Korea recently used what would be its largest ever intercontinental ballistic missile (ICBM) system in two secretive launches, likely paving the way for a resumption of long-range tests, U.S. and South Korean officials said.
North Korea froze its ICBM and nuclear tests in 2017 after launching its first missiles capable of reaching the United States. It has also not tested a nuclear weapon since then but leader Kim Jong Un has warned of a return to testing both.
The escalation in North Korea tensions comes as South Korea on Wednesday elected a new conservative president.
Yoon Suk-yeol has said preemptive strikes may be needed to counter any imminent attack by the North and has vowed to buy American THAAD missile interceptors, while remaining open to restarting stalled denuclearisation talks.
Reclusive North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.
In launches on Feb. 27 and March 5, North Korea did not specify what missile was used, but said they tested components for reconnaissance satellites Kim said would soon be launched to monitor military activity by the United States and its allies.
"The purpose of these tests, which did not demonstrate ICBM range, was likely to evaluate this new system before conducting a test at full range in the future, potentially disguised as a space launch," Pentagon spokesman John Kirby said in a statement.
The U.S. Treasury, which has imposed a range of sanctions on North Korea over its weapons programmes, will announce new actions on Friday to help prevent North Korea "accessing foreign items and technology that enable it to advance its weapons programmes", a senior U.S. administration official told reporters in Washington, speaking on condition of anonymity.
These steps would be followed by a range of further actions in coming days, the official added, without giving any details.
Japanese Prime Minister Fumio Kishida and Yoon said they had agreed to ramp up three-way ties with the United States in responding to North Korea's evolving military threat.
Japan is also considering imposing additional sanctions against North Korea, as well as other diplomatic options, Kishida told reporters after a phone call with the South Korean president-elect.