Asserting that America and its diplomacy are back, US President Joe Biden on Thursday said his administration will repair the relationship with allies and engage with the world once again. The US, he said, must meet the new moment accelerating global challenges -- from the pandemic to the climate crisis to nuclear proliferation -- challenging the will only to be solved by nations working together and in common. "We cannot do it alone," he said. In his maiden address to the employees of the State Department, the president said he has come to the building to send a clear message to the world: America is back. America is back. Diplomacy is back.