Former US President George W. Bush said he won't criticize President Barack Obama because his successor "deserves my silence," and said he plans to write a book about the toughest decisions he made in office. Bush declined to critique the Obama administration Tuesday in his first speech since leaving office. Former Vice President Dick Cheney said this week that Obama's overturning of Bush administration terrorism-fighting initiatives are making Americans less safe. "I'm not going to spend my time criticizing him," Bush said. "There are plenty of critics in the arena. He deserves my silence." Bush said he wants Obama to succeed and said it's important that he has support. Fiery conservative talk-show host Rush Limbaugh has said he hoped Obama would fail, in remarks that were denounced by critics who said Limbaugh was rooting for the US to fail.