The failed face-to-face talks with President Donald Trump raise a doubt whether the US is committed to improving relations with North Korea, its leader Kim Jong-un said, while promising to beef up the nation’s defense.

Pyongyang will give the US till the end of the year to drop “its current calculation method” with regards to bilateral talks and come up with “a correct posture” instead, Kim said, the state-run KCNA news agency reported on Saturday. In that case, North Korea will consider holding a third summit with President Trump sometime in the future, he explained.

Addressing the nation’s parliament, Kim said that his talks with US President Donald Trump in February raised “a strong question” whether the country was right in making concessions. The meeting, which was cut short by the White House and ended without an agreement, also cast doubt on the “true willingness” of Washington to improve relations with North Korea.

According to Kim, the problem lied in the “American-style way of dialogue” which amounted to making “unilateral” demands without being ready to “sit face-to-face with us and settle the problem.”

As Pyongyang waits for the US to change its stance, it will “keep increasing the defense capabilities,” the North Korean leader stressed. He didn’t specify what branches of the military will be strengthened and how.

Donald Trump, meanwhile, wrote on Twitter that another meeting with Kim “would be good in that we fully understand where we each stand.” The relationship between the leaders “remains very good, perhaps the term excellent would be even more accurate,” he added.

The president’s tone was in contrast with the stricter stance of US Secretary of State, Mike Pompeo, who earlier said that he wanted to “leave a little space” for easing the sanctions on Pyongyang but affirmed that the restrictions would largely remain in place as long as the US deems North Korea a nuclear threat.

Trump and Kim met for the first time in Singapore last year. They agreed to pursue peace, and North Korea pledged to work toward “complete denuclearization” of the Korean Peninsula. In the months leading up to the talks, Pyongyang froze its nuclear and ballistic missile tests and demolished the only known nuclear test site.

The next round of talks, held in Hanoi, Vietnam, quickly fell apart. The US flatly rejected the proposal to partially lift the sanctions on North Korea in exchange to additional assurances that Pyongyang will not restart nuclear and ballistic missile tests. Trump’s National Security Advisor, John Bolton, later clarified that the White House found Kim Jong-un’s idea of a ‘step-by-step denuclearization’ unacceptable as well.

North Korean officials have since expressed a readiness to resume the nuclear and ballistic missile program if the US continues its aggressive policy toward the nation.