SEOUL, South Korea — The North Korean leader, Kim Jong-un, has vowed to build up his country’s nuclear arsenal as a “powerful deterrent” to the United States, state media reported, hours after President Trump said that “only one thing will work” in dealing with the isolated country.

Mr. Kim made his comments on Saturday at a meeting of the Central Committee of his ruling Workers’ Party, the official Korean Central News Agency reported on Sunday. He also reconfirmed his policy of simultaneously seeking progress in his nuclear weapons program and pushing for economic growth in the face of expanding international sanctions.

The remarks indicated that Mr. Kim had no intention of retreating under American pressure even as South Korean officials and analysts worry that the North will conduct a major weapons test to observe the anniversary on Tuesday of the founding of the Workers’ Party.

North Korea’s nuclear weapons are a “powerful deterrent firmly safeguarding the peace and security in the Korean Peninsula and Northeast Asia,” Mr. Kim was quoted as saying, citing “protracted nuclear threats of the U.S. imperialists.”