After the latest missile test "now no one can infringe our sovereignty and rights to survive and develop", Vice Chairman Pak Kwang-Ho of the party's decision-making Central Committee said, adding that the USA had been "jolted" at the strengthening of North Korea's nuclear force and could attempt to commit "robber-like" provocative acts.
The results are in from North Korea's latest missile test, and it looks as if the country's weapons program is advancing despite the US's best efforts.
Since taking office in June, Kang traveled to South Korea's most important neighbors - the United States, Russia and China - except for Japan.
Russian Foreign Minister Sergei Lavrov said Washington's approach was dangerously provocative.
Reports have speculated the nuclear test site will have to close because of the tremors, but 38 North said "complete abandonment of the test site as a whole remains unlikely".
Photos released by North Korean media show the launch process as supervised by the country's leader, Kim Jong Un, and reveal a new missile, the Hwasong-15, that is unlike anything previously seen from the nation.
"If the United States drops out of this deal, it won't be very credible in the eyes of those who are now requested to drop their (own) nuclear programme like North Korea", Lavrov said. "President Trump called President Xi this morning and told him that we've come to the point where China must cut off the oil for North Korea".
"We know they were building to this".
Trump has pledged more sanctions in response to the latest test and, at an emergency U.N. Security Council meeting late Wednesday, the United States warned North Korea's leadership would be "utterly destroyed" if war were to break out.
Nikki Haley, the U.S. ambassador to the United Nations. "We are stuck. We have to adapt to North Korea as a nuclear power, and we will actually".
USA sanctions against North Korea were bolstered last week after the Trump administration declared North Korea a state sponsor of terrorism.
A White House statement about the phone conversation between the U.S. and Chinese leaders said Mr Trump made clear "the determination of the United States to defend ourselves and our allies". The United States, which has 28,500 troops in South Korea as a legacy of the 1950-53 Korean War, denies any such intention.
China also suggested the North should stop the tests in return for a halt to U.S. military exercises - a proposal Washington has rejected in the past.
Russian Foreign Minister Sergey Lavrov said on Friday that a USA threat to destroy North Korea in the event of a war was "a bloodthirsty tirade" and military action against Pyongyang would be a big mistake.