Australia will build a nuclear-powered submarine fleet in a major new alliance with the US and Britain to counter the worrying rise of China in the Pacific. Prime Minister Scott Morrison on Thursday morning unveiled Australia's role in a landmark tripartite security group, known by the acronym 'AUKUS', to switch to nuclear-powered submarines with help from its two of its biggest allies. Mr Morrison was joined virtually for the announcement by US President Joe Biden and UK Prime Minister Boris Johnson in a historic joint press conference. The deal will mean Australia will walk away from its controversial deal to…