North Korea’s foreign minister said on Saturday that there was “no way we will denuclearize” without getting so-called trust-building concessions from the United States, an assertion that reflected a continuing divide over efforts to ease nuclear tensions on the Korean Peninsula.

“Without any trust in the United States, there will be no confidence in our national security, and under such circumstances there is no way we will unilaterally disarm ourselves first,” the North Korean minister, Ri Yong-ho, told the United Nations General Assembly.

Even so, hours later at a rally, President Trump praised the two countries’ improved relations, to the point of saying he and the North Korean leader “fell in love.”

“I was really being tough, and so was he,” Mr. Trump said Saturday of Kim Jong-un. “And we would go back and forth.” He added, to laughter from the crowd in Wheeling, W.Va.: “And then we fell in love, O.K.? No, really. He wrote me beautiful letters, and they’re great letters. We fell in love.”