In an unusual move, the entire US Senate is being called to the White House for a briefing on North Korea. <br/><br/>Washington has become increasingly concerned at North Korean missile and nuclear tests and threats to its neighbours and the US. <br/><br/>The briefing, involving 100 senators as well as Secretary of State Rex Tillerson and Defence Secretary James Mattis, is being held tomorrow.<br/>'<br/>White House officials regularly go to Congress to brief on national security matters, but it is unusual for the whole Senate to go to the White House. <br/><br/>Mr Trump has said North Korea's continued belligerence was destabilising the Korean peninsula.<br/>'<br/>Meanwhile, China, North Korea's main ally, has called for restraint from all sides and avoid actions that would increase tensions. <br/><br/>China's call came in a phone conversation between President Xi Jinping and President Donald Trump on Sunday.<br/>