SEOUL, South Korea — North Korea said on Tuesday that it was improving its nuclear arsenal in both “quality and quantity,” reaffirming that the country’s main nuclear complex, including its only disclosed uranium-enrichment plant, was in full operation.
North Korean scientists and engineers have made innovations “to guarantee the reliability of the nuclear deterrent in every way by steadily improving the levels of nuclear weapons with various missions in quality and quantity,” the state-run Korean Central News Agency quoted the director of the North’s Atomic Energy Institute as saying.
The director, who was not identified by name, was also quoted as saying that if the United States and its allies continue their “reckless hostile policy” toward the North, the country “is fully ready to cope with them with nuclear weapons any time.”
The threat, which was not an unusual one in North Korea’s state news media, came amid speculation from analysts in the region that the North’s young leader, Kim Jong-un, might mark the 70th anniversary of the founding of the country’s ruling Workers’ Party on Oct. 10 by showing off advances in its nuclear and long-range missile programs.
On Monday night, North Korea indicated that it was preparing to launch a new satellite into orbit for scientific purposes. It did not say when that would take place, but Washington and its allies have urged the North to refrain from such launches, which they consider a cover for developing an intercontinental ballistic missile.
Mr. Kim is believed to count the North’s arsenal of nuclear weapons and missiles as one of the proudest achievements of his family, which has ruled the impoverished country since its founding in 1948. For years, Washington has tried both sanctions and dialogue to persuade North Korea to give up its nuclear weapons and long-range missile development, to no avail.
Instead, North Korea in recent years has been renovating and expanding ts main nuclear complex in Yongbyon, north of Pyongyang, the capital, as well as its primary satellite-launching site in Tongchang-ri near its northwestern border with China.
The state media report on Tuesday quoted the Atomic Energy Institute director as reaffirming that “all the nuclear facilities” in Yongbyon, including the uranium-enrichment plant and a 5-megawatt graphite-moderated reactor, “were rearranged, changed or readjusted” and were in “normal operation.”
North Korea is widely believed to have built at least several nuclear bombs using plutonium gleaned from the spent fuel of the Yongbyon reactor before it was shut down under a short-lived nuclear disarmament deal with Washington in 2007. In 2013, after the deal collapsed, North Korea said it had restarted the reactor, as well as a newly disclosed uranium-enrichment complex there.
That same year, Mr. Kim declared that his nuclear weapons were not a bargaining chip and called for expanding his country’s nuclear arsenal both in “quality and quantity” during a Workers’ Party meeting. He said the nuclear weapons would help his country focus on rebuilding its economy, dismissing warnings from Washington and Seoul that it would only deepen the country’s isolation and economic misery.
The restarting of the Yongbyon reactor and the operation of the uranium enrichment plant there were particularly worrisome for American officials because they provided the North with two sources of fuel for more nuclear bombs: plutonium and highly enriched uranium.
American and South Korean intelligence officials have closely monitored Yongbyon. Private research institutes, citing commercial satellite images of the site, have said that North Korea may be attempting to expand its uranium-enrichment capacities as well as trying to extract more plutonium from spent fuel.
North Korea has conducted three nuclear tests since 2006, the latest in February 2013. The renewed activities in Yongbyon raised concern that North Korea was significantly increasing its nuclear fuel stockpile. Western intelligence officials say that North Korea is trying to build, if it has not already, a nuclear warhead small enough to be mounted on a ballistic missile.
Historically, increased activities at Yongbyon have increased tensions on the divided Korean Peninsula. On Tuesday, both Washington and Seoul warned that a new satellite launching by North Korea would violate United Nations Security Council resolutions, which barred the country from developing or testing ballistic missile technologies.