North Korea's foreign minister said Monday that President Trump's latest statement was a declaration of war against his country.

"This is clearly a declaration of war," Foreign Minister Ri Yong Ho said through a translator in New York. "... The U.N. charter stipulates individual member states' rights to self-defense. Since the United States declared war on our country, we will have every right to make countermeasures, including the right to shoot down the United States' strategic bombers even when they're not yet inside the airspace border of our country."

North Korea has been trying to convince other governments to condemn Mr. Trump for vowing to "totally destroy" the country in his speech to the United Nations, CBS News correspondent Ben Tracy reports.

In a letter sent to foreign parliaments, North Korea called Mr. Trump's threat an "intolerable insult," North Korean state media reported, and the country's foreign minister had said Mr. Trump's words made North Korea's "rocket's visit to the U.S. mainland inevitable all the more."

It was not immediately clear which governments had been sent the letter, Tracy says, but it was part of what appeared to be a new approach of trying to turn Mr. Trump's threats to destroy North Korea against him.

This is a developing story and will be updated.

© 2017 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.