The United States wants direct access to Dr Abdul Qadeer Khan and President Bush, in his recent visit to Pakistan, told President Pervez Musharraf that US experts want to question the detained scientist, said BBC security correspondent.Speaking at a television programme on Wednesday, BBC security correspondent Gordon Correra was commenting on a Pakistan Foreign Office statement, which said that the Dr AQ Khan case had been closed and that there would be no further investigation into the matter. He said that such a statement by the Pakistani Foreign Office was an attempt to sweep things under the rug. "But this raises a very difficult question for Pakistan - how a chief scientist was able to leak nuclear secrets to countries like Iran and Libya," Correra said. He said that Khan supplied nuclear material and designs to Iran and the US wanted access to Dr Khan because only he could explain the history and purposes of Iran's nuclear program. "The question everyone is asking is that did Khan sell nuclear weapons designs, because only the answer to this question will explain whether Iran was after nuclear weapons or not," he said.