Pakistan has developed new illicit channels to upgrade its nuclear weapons program, despite efforts by the U.N. atomic watchdog to shut down all illegal procurement avenues, diplomats and nuclear experts said. Western diplomats familiar with an investigation of the nuclear black market by the U.N.'s Vienna-based International Atomic Energy Agency (IAEA) said this news was disturbing. While Pakistan appeared to be shopping for its own needs, the existence of some nuclear black market channels meant there were still ways for rogue states or terrorist groups to acquire technology that could be used in atomic weapons, they said. "General procurement efforts (by Pakistan) are going on. It is a determined effort," a diplomat from a member of the 44-nation Nuclear Suppliers Group (NSG) told Reuters on condition of anonymity. "This was discussed at an NSG meeting in Vienna last week."Nuclear experts said these channels involved new middlemen who had not played a role in earlier deals which came to light last year. "These are not the same people. They're new, which is worrying," said one Western diplomat. Pakistan is subject to sanctions against its atomic arms program as it has not signed the 1968 global nuclear Non-Proliferation Treaty (NPT). A diplomat from another NSG country that is a producer of technology usable in weapons programs said his country's customs agents were not surprised. "Our people are well aware of Pakistan's efforts to upgrade its centrifuge program." Asked if Pakistan was using the black market to upgrade its facilities, Foreign Ministry spokesman Jalil Abbas Jilani said in Islamabad: "To be honest, I don't have an update on that. Pakistan's nuclear capability is a reality which has to be reconciled, and obviously in order to maintain its capability Pakistan would make all the preparations." An IAEA spokeswoman declined to comment.