President-elect Barack Obama picked a national security team headed by former campaign rival Hillary Rodham Clinton and Bush administration holdover Robert Gates on Monday, and said he wants to consult with military commanders before settling on a firm timetable to withdraw U.S. combat troops from Iraq.

Obama said a newly completed agreement between Iraq and the Bush administration covering U.S. troop presence signals “a transition period in which our mission is changing” after a long war. The president-elect campaigned on a call to pull out most combat troops within 16 months of taking office, a period he said he still believes “is the right time frame.”

Obama named Clinton, a New York senator, as secretary of state and said Gates would remain as defense secretary, a post he has held for the past two years.

At a news conference, the president-elect also introduced retired Marine Gen. James Jones as White House national security adviser, former Justice Department official Eric Holder as attorney general, Arizona Gov. Janet Napolitano as secretary of homeland security and Susan Rice as ambassador to the United Nations.

The announcements rounded out the top tier of the team that will advise the incoming chief executive on foreign and national security issues in an era marked by wars in Iraq and Afghanistan and terrorism around the globe.

“I assembled this team because I am a strong believer in strong personalities and strong opinions,” he said.

“I think that’s how the best decisions are made. One of the dangers in a White House, based on my reading of history, is that you get wrapped up in group-think and everybody agrees with everything and there’s no discussion and there are no dissenting views. So I am going to be welcoming a vigorous debate inside the White House.”

“But understand, I will be setting policy as president. I will be responsible for the vision that this team carries out, and I will expect them to implement that vision once decisions are made.”

Obama’s announcements marked a shift in emphasis after a spate of appointments last week for his economic team, led by Timothy Geithner as treasury secretary.

He now has selected half the members of his Cabinet, and is filling out the top echelons of his administration at an unusually quick pace during his transition as he seeks to fulfill his goal of being able to “hit the ground running” when he takes the oath of office on Jan. 20.

Obama said his appointees “share my pragmatism about the use of power, and my sense of purpose about America’s role as a leader in the world.”

He introduced Clinton first, saying of his former presidential rival, “She possesses an extraordinary intelligence and toughness, and a remarkable work ethic. … She is an American of tremendous stature who will have my complete confidence, who knows many of the world’s leaders, who will command respect in every capital and who will clearly have the ability to advance our interests around the world.”

“I am proud to join you … and may God bless you and our great country,” the former first lady said in a brief turn at the lectern.

Gates’ presence in Chicago made him a visible symbol of the transition in power from the old administration to the new.

The president-elect, reprising a campaign vow, said he would give the military a new mission as soon as he takes office: “responsibly ending the war in Iraq through a successful transition to Iraqi control.” In his announcement remarks, he did not mention his oft-repeated pledge to withdraw most U.S. combat troops within 16 months, although he referred to it in response to a question several moments later.

Obama said he would make Rice, his pick for the U.N., a member of the Cabinet, an increase in stature from the Bush era.

Clinton, Holder, Napolitano and Rice all require confirmation by the Senate.

Jones, as a White House official, does not. Nor does Gates, already confirmed to his post.

At a news conference, Obama expressed sympathy for the victims of the terror attacks in Mumbai but declined to say whether the Indian government would be justified in pursuing terrorists in next-door Pakistan.

“This is one of those times when I have to reiterate there is one president at a time,” he said. “We’re going to be engaged in some very delicate diplomacy in the next days and weeks, and I think it would be very inappropriate of me to comment.”

Obama drew criticism during the campaign when he said the United States would be justified in pursuing al-Qaida terrorists in Pakistan if it had “actionable intelligence.”

In a debate on Feb. 26, then-candidate Clinton said of Obama, “Last summer, he basically threatened to bomb Pakistan, which I don’t think was a particularly wise position to take.”

Obama said disagreements sometimes are magnified during campaigns. As for his one-time rival, now Cabinet choice, he said, “I believe that there is no more effective advocate than Hillary Clinton for that well-rounded view of how we advance American interests.”

Clinton will give up her seat as a senator from New York to join the Obama Cabinet. Her appointment was preceded by lengthy negotiations involving her husband, the former president, whose international business connections posed potential conflicts of interests.

The former president agreed to disclose the donors to the foundation that built his library, as well as contributors to his international foundation.

Sen. Clinton had scarcely finished speaking when her husband issued a written statement. “She is the right person for the job of helping to restore America’s image abroad, end the war in Iraq, advance peace and increase our security, by building a future for our children with more partners and fewer adversaries, one of shared responsibilities and opportunities,” he said.

Gates said he was “mindful that we are engaged in two wars and face other serious challenges at home and around the world.”

“I must do my duty as they do theirs,” he said of the men and women in uniform in Iraq, Afghanistan and elsewhere. “How could I do otherwise?”

He said he was “honored to serve President-elect Obama.”

Gates’ appointment fulfilled a campaign promise by Obama, the naming of a Republican to his Cabinet.

Holder vowed to revitalize a Justice Department staggered by scandal during the Bush administration, both over the dismissal of federal prosecutors and the administration’s program of wiretapping as part of its war against terrorists.

Napolitano, like Clinton, must resign her current job. As a border state governor, she has experience with immigration issues, one of the pressing concerns that will confront the new administration.

Obama said Jones, his national security adviser, “will bring to the job the dual experience of serving in uniform and as a diplomat. He has commanded a platoon in battle, served as supreme allied commander in a time of war and worked on behalf of peace in the Middle East.”

The event was unlike those of last week, when Obama was the only one to speak. This time, he called on each of his appointees to make remarks, beginning with Clinton.

Vice President-elect Joe Biden said each member of the team shares the goals and the principles of the new administration that “strength and wisdom must go hand in hand,” and that America’s security “is not a partisan issue.”

Obama has settled on additional members of his Cabinet, although they have not yet been announced.

Among them are former Senate Democratic leader Tom Daschle to be his secretary of health and human services and New Mexico Gov. Bill Richardson to be commerce secretary.