North Korean Foreign Minister Ri Yong Ho on Monday slammed U.S. President Donald Trump's recent threats as a declaration of war against the country and said Pyongyang reserves the right to shoot down U.S. strategic bombers in self-defense.

"This is clearly a declaration of war," he told reporters in New York, referring to Trump's remark over the weekend saying that North Korean leader Kim Jong Un's leadership "won't be around much longer."

"Since the United States declared war on our county, we have every right to make countermeasures including the right to shoot down the United States strategic bombers" even when they are not flying in North Korean airspace, he said through an interpreter.

North Korea's top diplomat made the comments as Washington and Pyongyang have traded barbs for the past several days over the North's nuclear and ballistic missile programs.

Trump's labeling last week of Kim as "Rocket Man" on "a suicide mission" and his threat to "totally destroy" the country prompted a string of harsh words between the two countries.

Ri noted the sincere wish in the international community that the war of words will not turn into action, but went on to claim it was the United States who first declared war.

"In light of the declaration of war by Trump, all options will be on the operation's table of the supreme leadership of the DPRK," he said, referring to his country's formal name -- the Democratic People's Republic of Korea.

Ri was in New York to attend the U.N. General Assembly, at which he delivered a speech on Saturday stating that Pyongyang will take "merciless pre-emptive action" if there is any sign of a U.S. military attack on it, while asserting that Trump, not Kim, is the one on a "suicide mission."

Kim on Friday threatened to take the "highest-level" of retaliatory action against Trump, which Ri said "could be the most powerful detonation of an H-bomb in the Pacific Ocean."

U.N. Secretary General Antonio Guterres warned Monday that an escalation of rhetoric between the two countries increases the risk of miscalculations, his spokesman said.

"Fiery talk can lead to fatal misunderstandings. We want to reiterate that the only solution for this is a political solution and I would also reiterate the secretary general's call for statesmanship," Stephane Dujarric told reporters.

In defiance of U.N. Security Council resolutions, North Korea on Sept. 3 conducted its sixth and largest nuclear test, saying it was a hydrogen bomb that can be mounted on an intercontinental ballistic missile.

There is increasing speculation that Pyongyang may carry out yet another provocative act around the founding anniversary of its ruling Workers' Party of Korea on Oct. 10.

The U.N. Security Council unanimously adopted a resolution toughening sanctions against Pyongyang in response to its latest nuclear test.

Trump also announced Thursday new unilateral U.S. sanctions taking aim at North Korea's weapons programs by sanctioning banks and other entities or individuals that trade with the country.