The Moscow physicist who supervised construction of North Korea's nuclear complex said Tuesday the isolated Asian nation's nuclear experts are on a par with their former Russian comrades.At the same time, said Vladislav Kotlov, who headed building of North Korea's Yongbyon complex from 1963 to 1965, there is no evidence Pyongyang has used this expertise to build a nuclear weapon, despite reports to the contrary."The level of preparation of North Korean specialists is on the same level as that of Russian specialists, so today, that possibility of making nuclear weapons exists," Kotlov told a press conference. "But to say they are using these capabilities or pose some danger can be confirmed only after tests are conducted."U.S. Defense Secretary William Perry said in a recent interview, however, that the CIA estimates North Korea already possesses one and maybe two nuclear bombs.Kotlov, then a 30-year-old expert with a degree from a top Moscow physics institute, in 1963 led a team of 40 Soviet atomic experts and thousands of North Korean laborers in assembling the nuclear research complex.Kotlov's team also provided training for North Korean specialists. Others visited the U.S.S.R. for further education in nuclear physics. After the scientists left, the Soviet Union continued to send reactor fuel until 1990, and other Soviet specialists visited from time to time to provide technical assistance, he said.Today, Kotlov's creation, which has been expanded with several additional reactors since the mid 1960s, has become a diplomatic flashpoint, as many believe that North Korean President Kim Il-Sung is diverting fuel rods from the nuclear reactor to make weapons. North Korea has strenuously denied the accusations and said its Atomic Energy Research Center serves strictly peaceful purposes.Despite the potential for the North Korean leaders to develop weapons of mass destruction at the Yongbyon facility, Kotlov said he has no regrets about his role in establishing the facility. "I have no doubt that this complex is needed," said Kotlov. "Above all, it is an instrument for research."Kotlov, who also helped the Soviet Union construct nuclear reactors in Iraq and China, declined to say how long it would take a skilled team of scientists to assemble a nuclear bomb at a facility such as Yongbyon. Russia still has a friendship treaty with North Korea dating back to 1961, and two nuclear cooperation agreements are still on the books. Yet the agreements between the two countries have effectively lapsed, and Russians no longer work or consult with North Korea on the atomic facilities, according to Georgy Kairov, a spokesman for the Ministry of Atomic Energy."We definitely know that not a single specialist who worked on nuclear weapons production or who knows secret information which could be used abroad to create nuclear weapons has left our country," he said.Still, Russian nuclear experts are ready to resume their cooperation with North Korea, said Kairov, a specialist in nuclear weapons testing. "It's a political question, but as a technician involved in the use of atomic energy for peaceful purposes, I think it should be continued," he said. He added that Pyongyang must first fulfill all international nonproliferation demands before any collaboration could resume.