Seoul, South Korea — North Korea threatened Thursday to resume insulting President Trump and consider him a "dotard" if he keeps using provocative language, such as referring to its leader as "rocket man." Choe Son Hui, the first vice foreign minister, issued the warning via state media days after Mr. Trump spoke of possible military action toward the North and revived his "rocket man" nickname for North Korean ruler Kim Jong Un.

The comments came as prospects dim for a resumption of nuclear diplomacy between the two countries. In recent months, North Korea has hinted at lifting its moratorium on nuclear and long-range missile tests if the Trump administration fails to make substantial concessions in nuclear diplomacy before the end of the year.

Choe said Mr. Trump's remarks "prompted the waves of hatred of our people against the U.S." because they showed "no courtesy when referring to the supreme leadership of dignity" of North Korea. She said North Korea will respond with its own harsh language if Mr. Trump again uses similar phrases and shows that he is intentionally provoking North Korea.

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"If any language and expressions stoking the atmosphere of confrontation are used once again ... that must really be diagnosed as the relapse of the dotage of a dotard," Choe said.

On Wednesday, the North's military chief, Pak Jong Chon, also warned that the use of force against the North would cause a "horrible" consequence for the U.S. He said North Korea would take unspecified "prompt corresponding actions at any level" if the U.S. takes any military action.

During a visit to London on Tuesday, President Trump said his relationship with Kim was "really good" but also called for him to follow up on a commitment to denuclearize. "We have the most powerful military we ever had, and we are by far the most powerful country in the world and hopefully we don't have to use it. But if we do, we will use it," Mr. Trump said.

He added that Kim, "likes sending rockets up, doesn't he? That's why I call him rocket man."

CBS News "Face the Nation" moderator Margaret Brennan says the Trump administration will be preparing for a potential diplomatic crisis over the next three weeks ahead of North Korea's end-of-year deadline for a breakthrough in diplomacy. The U.S. is taking seriously the threat that North Korea could break its 18-month pause on nuclear or long-range weapons tests.

Administration officials would not say whether President Trump's revival of the "rocket man" moniker was a deliberate signal to the North of waning patience in Washington, but as Brennan notes, it appears to have gotten Pyongyang's attention, given the statements by North Korea in recent days.

North Korea's leader Kim Jong Un and President Donald Trump look on during a bilateral meeting in the Metropole hotel during a North Korea-U.S. summit in Hanoi, Vietnam, February 28, 2019. Leah Millis/REUTERS

In 2017, Mr. Trump and Kim traded threats of destruction as North Korea carried out a slew of high-profile weapons tests aimed at acquiring an ability to launch nuclear strikes on the U.S. mainland. The U.S. president said he would rain "fire and fury" on North Korea and derided Kim as "little rocket man," while Kim questioned Mr. Trump's sanity and said he would "tame the mentally deranged U.S. dotard with fire."

The two leaders have avoided such words and developed better relations after North Korea entered nuclear negotiations with the U.S. last year. Mr. Trump even said he and Kim "fell in love."

North Korea threatened the U.S. earlier this week with a "Christmas gift" unless the Trump administration agrees to significantly ease sanctions as part of any resumed nuclear talks. As CBS News correspondent Elizabeth Palmer reported, those talks have been stalled since February.

It was during a visit to London for a NATO summit this week that Mr. Trump used the phrase "rocket man" again, as he appeared to take the "Christmas gift" threat in stride. After he used the term, he added that he believed he still had "a very good relationship" with Kim.

The two men have met three times, starting with a summit in Singapore in June 2018. But their nuclear diplomacy has remained largely deadlocked since their second meeting in Vietnam in February ended without any deal due to disputes over U.S.-led sanctions on North Korea.

Trump's national security adviser Robert O'Brien said Thursday night in Washington the U.S. remains hopeful that a deal can be reached with North Korea.

"Kim Jong Un has promised to denuclearize the Korean Peninsula. We hope that he sticks to that promise, and we're going to keep at the negotiations and keep at the diplomacy as long as we think that there's hope there. And we do," O'Brien said Thursday night on Fox News Channel's "Special Report with Bret Baier."

"I don't want to say we're optimistic, but we have some hope that the Koreans will come to the table ... and we can get a deal."