CHICAGO -- Barack Obama promised "a new dawn of American leadership" in a troubled world Monday, announcing a strong-willed national security team headed by Hillary Rodham Clinton, who fought him long and bitterly for the presidency, and Robert Gates, the man who has been running two wars for George W. Bush.

President-elect Barack Obama, second from left, stands with Secretary of State-designate Sen. Hillary Rodham Clinton, D-N.Y. third from left, as National Security Adviser-designate Ret. Marine Gen. James Jones, far right, and Vice President-elect Joe Biden, far left, leave the stage at the end of a news conference in Chicago, Monday, Dec. 1, 2008. [Agencies]

The president-elect said he hadn't changed his mind about bringing most US combat troops home from Iraq within 16 months but added a cautionary note - he'll consult with his military commanders first.

While his new team may be a bit more centrist - some war opponents might even say hawkish - than many Obama supporters might prefer, he said the withdrawal timetable he emphasized in the presidential campaign is still "the right time frame."

At a Chicago news conference, Obama also tapped top advisers Eric Holder as attorney general and Susan Rice as ambassador to the United Nations. He named Arizona Gov. Janet Napolitano to be homeland security secretary and retired Marine Gen. James Jones as White House national security adviser.

The choices had been telegraphed days earlier but were remarkable all the same - still another major turn in Clinton's extraordinary career, a show of faith in Gates and action to support Obama's frequent talk of desiring robust debate among seasoned, opinionated people in his inner circle.

Denouncing White House "group think," Obama signaled a break from President Bush's tendency toward an insular management style and go-with-the-gut diplomacy.

"The time has come for a new beginning," said Obama, flanked by flags on a stage with Vice President-elect Joe Biden and his six newest appointees. While Gates will stay at the Pentagon, Obama said the military's new mission will be "responsibly ending the war in Iraq through a successful transition to Iraqi control."