WASHINGTON, United States - Excited crowds poured into downtown Washington on Monday for Barack Obama's second inauguration as US president, anchored on a call for America to unite despite ugly political divides.

Barack Hussein Obama will raise his right hand and place his left on Bibles once owned by Martin Luther King and Abraham Lincoln and swear the oath of office before mustering for four years threatened by strife at home and abroad.

The 44th US president, and the first African American to hold the office, launched his second term with a private swearing-in ceremony on Sunday, before basking in the full pomp of his office with public celebrations Monday.

Obama will set the rhetorical tone for the remainder of his presidency with an inaugural address to a crowd expected to reach half a million, will headline a parade and then waltz with the first lady at glittering inaugural balls.

Watch Obama's second Presidential inauguration here (live stream starts at 11pm MNL time), courtesy of the PBS NewsHour:

Tune in to our live blog below. Or click through to our 57th US Presidential Inauguration Live Blog.