President Donald Trump and North Korean leader Kim Jong Un take a walk after their first meeting at the Sofitel Legend Metropole Hanoi hotel, in Hanoi, Feb. 28, 2019. Kim said he’s open to having a third summit with Trump if the United States could offer mutually-acceptable terms for an agreement by the end of the year. Credit: Evan Vucci | AP

TOKYO — North Korean leader Kim Jong Un said he would be prepared to meet President Donald Trump for a third summit, but only if the United States fundamentally changes its approach. He also warned that his patience is running out.

In a speech to the Supreme People’s Assembly in Pyongyang, Kim offered no hints of new concessions or ideas from his regime after the failure of February’s summit, putting the blame squarely on the United States and throwing the ball into Washington’s court.

Experts said the speech kept the window open for diplomacy but didn’t offer much hope for substantive progress. Meanwhile, North Korea continues to expand its nuclear arsenal.

“If the U.S. adopts a correct posture and comes forward for the third DPRK-U.S. summit with a certain methodology that can be shared with us, we can think of holding one more talk,” Kim said, referring to his country’s official name, the Democratic People’s Republic of Korea.

But Kim said that he did not feel the need to meet Trump just to secure sanctions relief and that the prospect of another summit like February’s meeting in Hanoi was “not inviting.”

“Anyway, we will wait for a bold decision from the U.S. with patience till the end of this year, but I think it will definitely be difficult to get such a good opportunity as the previous summit,” he said.

But Kim told the assembly, the regime’s equivalent of a parliament, on Friday that the United States was miscalculating if it thinks it can bring his government to its knees through sanctions and “maximum pressure,” adding that Washington was making suggestions that are “absolutely impractical.”

“If it keeps thinking that way, it will never be able to move the DPRK even a knuckle, nor gain any interests no matter how many times it may sit for talks with the DPRK,” Kim said in remarks carried by the state Korean Central News Agency on Saturday.

At the Hanoi summit, North Korea offered to close down a key nuclear site in return for the lifting of almost all of the economic sanctions imposed by the United Nations Security Council. Trump asked Kim to “go big” by turning over his entire nuclear, chemical and biological arsenal and production capability in return for a “bright future” economically.

Trump appears convinced that North Korea has tremendous economic potential and seems wedded to the notion that Kim might abandon his nuclear program in return for U.S. help in realizing that potential. But experts also see the hand of national security adviser John Bolton in the administration’s maximalist demands, advancing what amounts to an unrealistic ultimatum.

In tweets Saturday, Trump described his relationship with Kim as “excellent” and said he would be open to a third summit to “fully understand where we each stand.” But Trump offered no new proposals.

Secretary of State Mike Pompeo said the United States had continued to have “conversations” with North Korea even after Hanoi.

“I’m confident that what we did in Hanoi put us in a better place to move forward,” he told reporters on a trip to South America. “Chairman Kim made a commitment, he made the commitment to me personally no fewer than half a dozen times and to President Trump that he wanted to denuclearize.”

In his speech, Kim also complained that the United States had resumed military exercises with South Korea this year, despite what he said was a direct commitment by Trump to suspend them.

“These seriously rattle us,” he said. “As wind is bound to bring waves, the U.S. open hostile policy toward the DPRK will naturally bring our corresponding acts.”

But Kim did not spell out what his response might be, after ominously warning in a New Year’s Day speech that he might be forced to seek a “new way” if the United States did not drop its unilateral demands and sanctions pressure.

He also reiterated that his problem was with Trump’s administration, not the president.

“But as President Trump keeps saying, the personal ties between me and him are not hostile like the relations between the two countries and we still maintain good relations, as to be able to exchange letters asking about health anytime if we want,” he said.

Van Jackson, a former Pentagon official who teaches at Victoria University of Wellington in New Zealand, said time is on North Korea’s side.

“A Trump-Kim personal relationship benefits Kim and North Korea, not the United States,” he said. “So, it’s no surprise that Kim is open to the pomp and pageantry of a third summit.”

But Jackson said there was no sign that Kim was willing to make the nuclear concessions demanded by Trump’s “uber-hawks,” implying that the summit-driven process will continue to drag out without bringing nuclear stability to the Korean Peninsula.

Ankit Panda, an adjunct senior fellow in the Defense Posture Project at the Federation of American Scientists, also saw no signs of a change in Kim’s negotiating position — that North Korea expects to see “corresponding” concessions from the United States in return for its moratorium on nuclear and missile testing announced last year.

The only difference now is that Kim has given the United States until the end of the year.

“A lack of U.S.-North Korea progress in the meantime will allow Kim to continue the quantitative expansion of his nuclear forces,” Panda said. “He doesn’t need to test nuclear devices or missiles to continue building his forces out.”

South Korean President Moon Jae-in met with Trump in Washington on Thursday in a bid to keep the dialogue alive, and the presidential Blue House said in a statement Saturday that it would “do what we can in order to maintain the current momentum for dialogue, and help negotiations between the U.S. and North Korea resume at an early date.”

But Kim was sharply critical of the South Korean government, arguing that it should not act as a “mediator” or “booster” for hostile forces, but instead act in the interests of the whole Korean Peninsula.

There will be no improvement in North-South ties unless South Korea ends military exercises with the United States, he said, “and unless a fundamental liquidation is put to the anachronistic arrogance and hostile policy of the U.S., which creates a deliberate hurdle in the improvement of ties while coming forward with unilateral gangsterlike demands.”

Cheon Seong-whun, who served as national security adviser to former conservative South Korean President Park Geun-hye, said he sees a “deadlock.”

“Kim Jong Un says he will stick to his position and is pressuring Washington to make concessions,” he said. “It’s a non-starter.”

Washington Post writers Min Joo Kim, John Hudson and Brian Murphy contributed to this report.