President Donald J. Trump said he would reach out to North Korean leader Kim Jong-un, raising the possibility of a restart their bromantic diplomacy five years after their first round of talks attracted global attention but did little to reduce Mr Kim’s growing nuclear threat.

“He liked me and I got along with him,” said Mr. Trump, during an interview with Fox News host Sean Hannity, after saying he would again reach out to Mr. Kim in his second term. “He is not a religious fanatic. He just happens to be a smart guy.”

Comments of Mr. Trump, broadcast on Thursday night, was the first time he expressed his intention to reopen diplomacy with Mr. Kim since he took office on Monday. During his first mandate, Mr. Trump and Mr. The Kims made history when they held the first summit between their nations, which are technically still at war. But their relationship soured after their three high-profile meetings failed to produce any progress.

It is unclear whether and how Mr. Kim, emboldened by a stronger alliance with Russia and his own country’s military advancement, responded to the overtures this time. Since Mr. Trump last met with Mr. Kim five years ago, North Korea’s missile capabilities have expanded and he may demand a higher price for concessions on his nuclear program, analysts say.

Mr. Trump expressed interest in the North Korean leader during his campaign, saying at one point that “it’s nice to get along when somebody has a lot of nuclear weapons.” Hours after his inauguration, he also told reporters that Mr. Kim was a “nuclear power,” a shift from Washington’s long-standing refusal to recognize North Korea as such.

Officials in South Korea, America’s ally in a pinch domestic political crisis after the impeachment of their leader, they feared that Mr. Trump’s return could once again put the Korean Peninsula on a diplomatic rollercoaster ride.

During his first mandate Mr. Trump and Mr. Kim first exchanged personal insults and threats of nuclear war. They then shook hands and held three meetings between 2018 and 2019. At one point, Mr. Trump declared on social media that there is “no longer a nuclear threat from North Korea” and that he has “fallen in love” with Mr. Nods.

Those talks, however, ended without agreement on how to scale back North Korea’s nuclear and ballistic missile programs or when the United States should ease sanctions imposed on the country. Mr. Kim has vowed not to engage Washington in dialogue again and has doubled down on building and testing nuclear-capable missiles.

Now South Korean analysts and officials fear that Mr. Trump could make a deal with Mr. Kim in which North Korea would give up its long-range missiles, but not its nuclear weapons, in exchange for the lifting of sanctions.

Mr Trump’s recent statement describing North Korea as a nuclear power contradicted a longstanding agreement between Washington and Seoul that North Korea should never be accepted as such.

“We cannot grant North Korea the status of a nuclear power,” South Korea’s defense ministry said in a statement after Trump’s comments.

Despite Mr Trump’s flattering comments about Mr Kim, it was unclear whether the dictator would warm to the idea of ​​a re-wooing. After the failure of the first round of meetings, Mr. Kim has championed a new “multipolar” global order, signing a mutual defense pact with Moscow last year and sending weapons and an estimated 12,000 troops to help Russia in its war against Ukraine.

Despite heavy losses in the war against Ukraine, North Korea was preparing to send new troops to Russia, the South Korean military said on Friday.

China has long been the only major buffer between North Korea and American-led international efforts to tame its regime’s military ambitions. In exchange for helping Russia in the war against Ukraine, Mr. Kim enlisted Moscow as another key ally to protect his country from US pressure.

North Korea had not commented on Mr Trump’s election or inauguration until Wednesday, when its state media carried a two-sentence report.

The regime, however, launched missiles from its east coast in the days before the inauguration. And it is preparing to launch more missiles, according to South Korea’s military, including long-range ballistic missiles powerful enough to reach the continental United States, which most worries U.S. defense officials.

North Korea’s state media reported Friday that the national parliament this week passed budgets for this year that will “ensure the acceleration of significant change in national defense capabilities.”

Mr. Kim is likely to wait until the Workers’ Party meeting in June or another parliamentary gathering in September to react to Trump’s overture, said Hong Min, a senior analyst at the Korea Institute for National Unification in Seoul.

“It will react after assessing the seriousness, intent and calculations of the Trump administration behind its approach to North Korea,” Mr. Hong said.