WikiLeaks has appealed for leaked White House documents before President Barack Obama leaves office, as its founder Julian Assange again denied Russia was the source of hacked Democratic party emails that hurt Hillary Clinton’s bid for the US presidency. “System admins: Don’t let the White House destroy US history again! Copy now, then send to WikiLeaks at your leisure,” the secret-spilling website announced on Twitter, shortly before Assange gave an in-depth interview to US network Fox. “We are issuing a US$20,000 reward for information leading to the arrest or exposure of any Obama admin agent destroying significant records,” the tweet said.