North Korean leader Kim Jong Un has called U.S. President Donald Trump "deranged" and said he will "pay dearly" for threating to "totally destroy" North Korea.
Kim made the remarks on September 22 in response to recent U.S.-led sanctions efforts and a threat Trump made on September 19 in a speech to the United Nations General Assembly.
Trump on September 21 signed an executive order expanding sanctions on North Korea by targeting individuals and companies that trade with Pyongyang.
Trump told reporters it was unacceptable that entities support the North Korean regime financially.
He said the executive order will cut off revenue that funds Pyongyang's efforts to develop nuclear weapons.
North Korea has launched dozens of missiles under Kim's leadership as it accelerates a weapons program aimed at developing the ability to target the United States with intercontinental ballistic nuclear missiles.
Kim on September 22 said Trump should "exercise prudence in selecting words and be considerate of whom he speaks to when making a speech in front of the world."
"I will make the man holding the prerogative of the supreme command in the U.S. pay dearly for his speech calling for totally destroying [North Korea]," he said.
South Korean media later reported that North Korea's top diplomat said his country may test a hydrogen bomb in or over the Pacific Ocean to fulfill Kim's vow to take the "highest-level" action against the United States.
Trump on September 19 called on members of the UN General Assembly to take a harder line against threats posed by North Korea, referring to Kim as "Rocket Man" and saying he was on a "suicide mission."
South Korean President Moon Jae-in called on September 21 for the North Korean nuclear crisis to be handled in a "stable manner."
Moon told the General Assembly that while sanctions were needed to bring Pyongyang to the negotiating table, Seoul was not seeking North Korea's collapse.
The UN Security Council has imposed several rounds of sanctions on North Korea over its nuclear weapons and ballistic missile programs.
Pyongyang warned on September 18 that more sanctions and pressure will only make it accelerate its nuclear program.
In announcing the new sanctions, Trump said China's central bank had ordered banks to stop doing business with North Korea and that the measures will also target shipping and trade networks.
Trump said his order gave the U.S. Treasury discretion to sanction foreign banks that conduct transactions tied to deals with North Korea.