Washington | Donald Trump's dismissal of his hawkish national security adviser John Bolton complicates Scott Morrison's trip to the White House next week because it removes a key figure capable of ensuring the official visit runs smoothly, a top former Bush administration official has warned.

Michael Green, who served on the President George W Bush's National Security Council as lead official for Australian affairs, said Mr Bolton's sudden departure on Tuesday (Wednesday AEST) is "going to make the whole Morrison trip really interesting".