Watch live as Pete Buttigieg speaks at the United States Conference of Mayors (USCM) on Friday, 19 January, at the Capital Hilton Hotel in Washington, DC.

       The USCM is the official non-partisan organisation of cities with populations of 30,000 or more.

       More than 1,400 cities in the US fit this criteria, and each is represented in the conference by its chief elected official - the mayor.

       It began in the Great Depression in 1932, when Detroit mayor Frank Murphy invited US mayors to his city to address common problems caused by the economic crisis.

       The conference is an opportunity for mayors to engage directly with the president and Congress on the most pressing issues of the day.

       The US Secretary of Transportation's appearance comes after the Secretary of State, Antony Blinken, addressed the conference.