Joe Biden's condemnation of this week's North Korean missile launches risked provoking further weapons tests, a top regime official said on Saturday after Pyongyang's first substantive provocation since the US president took office.
The nuclear-armed North has a long history of using weapons tests to ramp up tensions, in a carefully calibrated process to try to forward its objectives.
Pyongyang had been biding its time since the new administration took office in Washington, not even officially acknowledging its existence until last week.
But on Thursday it launched two weapons from its east coast into the Sea of Japan, known as the East Sea in Korea.
Following the launch, Biden labelled the test a violation of UN resolutions and advised the isolated state against ramping up military testing, warning that "there will be responses if they choose to escalate."
Ri Pyong Chol, a leading official in North Korea's missile programme who supervised the test, said the president's comments had revealed his "deep-seated hostility" to the regime.
"Such remarks from the US president are an undisguised encroachment on our state's right to self-defence and provocation to it," Ri said in a statement published by state media outlet KCNA.
Ri said Pyongyang was expressing its "deep apprehension over the US chief executive faulting the regular testfire, (an) exercise of our state's right to self-defence, as the violation of UN 'resolutions.'"
"If the US continues with its thoughtless remarks without thinking of the consequences, it may be faced with something that is not good," he added, warning that North Korea was prepared to "continue to increase our most thoroughgoing and overwhelming military power."
- 'Tactical guided projectile' -
Pyongyang has made rapid progress in its capabilities under leader Kim Jong Un, testing missiles capable of reaching the entire continental United States as tensions mounted in 2017.
North Korea has reported that the Thursday launch, its first substantive affront since Biden came to office, was a test of a new "tactical guided projectile" with a solid-fuel engine.
Japanese Prime Minister Yoshihide Suga called the two weapons launched from North Korea's east coast ballistic missiles, which it is banned from developing under UN Security Council resolutions.
A UN sanctions committee focused on nuclear-armed North Korea has asked its experts to investigate the test and European members of the Security Council have requested an urgent meeting to discuss North Korea.
Thursday's launch, and an earlier test of short-range, non-ballistic missiles at the weekend, came after joint exercises by the US and South Korean militaries and a visit to the region by US Secretary of State Antony Blinken and Defense Secretary Lloyd Austin.
During their trip to Seoul and Tokyo, Blinken repeatedly stressed the importance of denuclearizing North Korea.
Biden's response demonstrates a change of tone from his predecessor Donald Trump, who engaged in an extraordinary diplomatic bromance with North Korean leader Kim Jong Un and last year repeatedly played down similar short-range launches.
Biden administration officials say they have sought to reach out to Pyongyang through several channels but have received no response so far.