President-elect Barack Obama on Monday tapped his toughest primary rival, Sen. Hillary Rodham Clinton (D-N.Y.), to become Secretary of State.

In glowing remarks, Obama commended the woman he beat for the Democratic presidential nomination as a friend and colleague who “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 capitol; and who will clearly have the ability to advance our interests around the world.”

Clinton thanked Obama for the honor of being appointed and vowed to give “her all” to the job. While she said it would be very difficult to leave the Senate, where she has served since 2001, becoming secretary of State would best allow her to serve the country.

Obama and Clinton will face a number of serious challenges on foreign policy, chief among them the continued American presence in Afghanistan and Iraq. Moving forward in both countries will require international help, and Clinton will be on the frontline in lobbying reluctant nations to commit to Afghanistan in particular.

Clinton noted that the “fate of our nation and the future of our children” depend on tackling global challenges and that the key to solving current problems is to find more friends and reduce the number of enemies.

Clinton’s husband, former President Bill Clinton, reacted to the nomination by saying: “As an American, I am thankful that President-elect Barack Obama has asked Hillary to be Secretary of State and that she has accepted.  As her husband, I am deeply proud.”

Bill Clinton added that she is the “right person for the job.”

“She has already earned the respect of foreign leaders and diplomats through her work to promote human rights and the empowerment of women through access to education, healthcare and economic opportunity,” Bill Clinton stated. “And Americans know, from her leadership in the Senate on national security, that she will always put the security, values and the interests of our people first.”

The bruising primary battle between Clinton and Obama was not decided until after Obama won a decisive victory over Clinton in the May 6 North Carolina primary. That win combined with a narrow loss to Clinton in Indiana led to the end of a race that deeply divided the Democratic Party, but Clinton still did not conceded until a month later.

Overall, Clinton won 1,639.5 pledged delegates to Obama's 1,766.5. She also won 23 states and territories, including California, New York and Florida.

The two clashed memorably over foreign policy during their primary fight, with Obama criticizing Clinton’s vote backing the Iraq War. Clinton, for her part, criticized Obama’s statement that he would meet with the leaders of hostile regimes with no preconditions.

After the battle, however, Clinton helped unite the party behind Obama by campaigning furiously across the country for the party's nominee.

The president-elect also announced that he would retain Secretary of Defense Robert Gates, named retired Gen. Jim Jones as National Security Adviser, Eric Holder as Attorney General, Arizona Gov. Janet Napolitano (D) as Homeland Security secretary and Susan Rice as ambassador to the United Nations.

“In this uncertain world, the time has come for a new beginning – a new dawn of American leadership to overcome the challenges of the 21st century, and to seize the opportunities embedded in those challenges,” Obama stated.

“To succeed, we must pursue a new strategy that skillfully uses, balances, and integrates all elements of American power: our military and diplomacy; our intelligence and law enforcement; our economy and the power of our moral example,” the president-elect added. “The team that we have assembled here today is uniquely suited to do just that. They share my pragmatism about the use of power, and my sense of purpose about America’s role as a leader in the world.”

Vice President-elect Joe Biden said Obama’s national security team “is poised to recapture the totality of America’s strength.”