WASHINGTON - The United States said Monday that even though the release of Pakistani nuclear scientist AQ Khan was the decision of an independent court, it had voiced its concern over the development and would follow up. At the same time, State Department Spokesman Robert Wood rejected a suggestion that by releasing Dr Khan, Pakistan was trying to blackmail the United States. "I don't think the Government of Pakistan is trying to blackmail us. They know our concern about AQ Khan, and as I've said over and over again, we will continue to make that case, and we want to do what we can to make sure that that network can in no way re-establish itself and continue the activities that it was once undertaking," he said while responding to a question at the regular news briefing. "Pakistan has a constitution. It has an independent judiciary," Wood added while answering a question about the status of the country's judiciary. "Well, look, this was a court decision that was taken. We have to deal with that fact," he said. The spokesman said the US is concerned on the release of the scientist due to his past activities and its embassy in Islamabad has been in touch with the Government of Pakistan on this issue. The US special representative for Afghanistan and Pakistan, Richard Holbrooke, also was expected to raise the issue during talks in Islamabad with Pakistani officials as part of his tour of the region, Wood said. "We're going to do what we can to try to make sure that the types of activities that have been undertaken in the past don't continue," he told reporters. "He remains a potential proliferation risk," he added. Last month, the United States slapped sanctions on Khan and a dozen others as well as three private companies because of their involvement in the nuclear proliferation network associated with the Pakistani scientist. Those sanctions followed a multiyear US government review of information regarding what it said was Khan's international network for the proliferation of nuclear equipment and know-how.