TOKYO — Kim Jong-un, North Korea’s leader, said Tuesday that he was willing to have a second summit meeting with President Trump, but he paired the offer with a threat that if international sanctions against his country were not lifted, the North would “have no choice” but to return to nuclear confrontation.

“I am willing to meet the United States president at any time for the betterment of our international community,” Mr. Kim said in his New Year’s Day speech, broadcast on North Korea’s state-run television. “However, if the United States does not keep its promise in our international community and misinterprets our patience and intention and continues with the sanctions, then we have no choice for the sake of our national interest and peace of the Korean Peninsula but to come up with new initiatives and new measures.”

Wearing a suit and tie and sitting in an overstuffed leather armchair in a book-lined room, Mr. Kim offered a largely motivational speech about the need to strengthen the North Korean economy. But he took the opportunity to reiterate a demand that South Korea cease all military drills with “other foreign sources.”

“Those should be completely stopped,” Mr. Kim said. “That is our stance.”

There were sparse direct references in the speech to denuclearization. But Mr. Kim said the country would not be willing to take further steps toward removing its nuclear weapons unless the United States reciprocated.