US President Donald Trump sought help from Chinese President Xi Jinping to win re-election, ex-National Security Adviser John Bolton's new book says. Mr Bolton says Mr Trump wanted China to buy agricultural produce from US farmers, according to details of the forthcoming book previewed by US media. He also says Mr Trump "remained stunningly uninformed on how to run the White House". The Trump administration is trying to block the book from going on sale. Speaking to Fox News, Mr Trump said of Mr Bolton: "He broke the law. This is highly classified information and he did not have approval." "He was a washed-up guy," the president added. "I gave him a chance." John Bolton joined the White House in April 2018 and left in September the following year, saying he had decided to quit. President Trump, however, said he had fired Mr Bolton because he disagreed "strongly" with him. He is known as a foreign policy hardliner and also served in the administration of President George W Bush. As national security adviser, he was the top counsellor to the US president on security matters at home and abroad. Mr Bolton's 577-page tome, The Room Where It Happened, is due to go on sale on 23 June. But on Wednesday night, the Department of Justice sought an emergency order from a judge to stop the book's release. The publisher, Simon & Schuster, said in a statement: "Tonight's filing by the government is a frivolous, politically motivated exercise in futility." It said hundreds of thousands of copies of the book had already been distributed around the world and the injunction would accomplish nothing. Mr Trump's Democratic challenger in this November's election, Joe Biden, said in a statement about the book: "If these accounts are true, it's not only morally repugnant, it's a violation of Donald Trump's sacred duty to the American people."