WASHINGTON (AP) — Declaring "our journey is not complete," President Barack Obama took the oath of office for his second term before a crowd of hundreds of thousands Monday, urging the nation to set an unwavering course toward prosperity and freedom for all its citizens and protect the social safety net that has sheltered the poor, elderly and needy.

"Our country cannot succeed when shrinking few do very well and a growing many barely make it," Obama said in a relatively brief, 18-minute address. "We believe that America's prosperity must rest upon the broad shoulders of a rising middle class," he added, echoing his calls from the presidential campaign that catapulted him to re-election.

The president declared a decade of war is ending, as is the economic recession that consumed much of his first term.

He previewed an ambitious second-term agenda, he devoted several sentences to the threat of global climate change and said that failure to confront it "would betray out children and future generations." Obama's focus on climate change was notable given that he barely dealt with the issue in his first term.

In an era of looming budget cuts, Obama said the nation has a commitment to costly programs such as Medicare, Medicaid and Social Security. "These things do not sap our initiative, they strengthen us," he said.

Sandwiched between the bruising presidential campaign and continuing fiscal fights, Monday's inaugural celebrations marked a brief respite from the partisan gridlock that has consumed the past two years.

Standing in front of the flag-bedecked Capitol, he implored Washington to find common ground over his next four years. And seeking to build on the public support that catapulted him to the White House twice, the president said the public has "the obligation to shape the debates of our time."

"Not only with the votes we cast, but with the voices we lift in defense of our most ancient values and enduring ideals," Obama said.

Moments earlier, Obama placed his hand on two Bibles — one used by the Rev. Martin Luther King Jr. and the other used by Abraham Lincoln — and recited the brief oath of office. Michelle Obama held the Bibles, one on top of the other, as daughters Malia and Sasha looked on.

Vice President Joe Biden was also sworn in for his second term as the nation's second in command.

Monday's oats were purely ceremonial. The Constitution stipulates that presidents begin their new term at noon on Jan. 20, and in keeping with that requirement, Obama was sworn in Sunday in a small ceremony at the White House.