Condoleezza Rice (search) has been nominated to lead U.S. diplomatic efforts during President Bush's second term, replacing Colin Powell (search) as secretary of state, the commander in chief announced Tuesday.

"Condoleezza Rice is already known to all Americans and to much of the world. During the last four years, I've relied on her counsel, benefited from her great experience and appreciated her sound and steady judgment, and now I'm honored she's agreed to serve in my Cabinet," Bush said at the White House in announcing her nomination.

Saying the secretary of state is "America's face to the world," Bush said the international community, in Rice, will see the "strength, grace and decency" of the United States.

Asking for quick Senate confirmation, Bush added: "The nation needs her."

But, he told reporters jokingly, "as many of you know, Condi's true ambition is beyond my power to grant -- she'd really like to be the commissioner of the National Football League. I'm glad she put those plans on hold again."

Rice, who teared up a little as Bush was singing her praises, said she has great respect for the men and women in the State Department and will work to provide them with all the tools necessary to carry out their duties.

"I look forward with the consent of the Senate to pursuing your hopeful and ambitious agenda as secretary of state. Mr. President, it is an honor to be asked to serve your administration and this country once again," Rice said following Bush's announcement.

"Let me say that in my 25 years of experience in foreign affairs, both in and out of government, I have come to know the men and women of the Department of State. I have the utmost admiration for their skill, their professionalism," she continued.

Powell, who Bush on Tuesday called "one of the most admired and effective diplomats" in America's history, announced his resignation on Monday, saying he had never intended to stay more than one term but would stay on until a replacement was named.

"He has been tireless and selfless and principled and our entire nation is grateful to his lifetime of service," Bush said of Powell.

Rice, considered more of a foreign policy hard-liner than Powell, whom she calls a "dear friend and mentor," has been Bush's national security adviser for four years.

"I think in every way it's a fine appointment and with her deputy, Dr. [Stephen] Hadley (search), he will simply be carrying on very much what she did," former defense secretary, Caspar Weinberger, told FOX News. "I think it's a transition that was not unexpected, but I didn't think it's going to make any big difference, policy-wise."

Hadley, Bush's current deputy national security adviser, will replace Rice.

Hadley first worked on the National Security Council under President Ford. He has taken the blame for erroneous statements about Iraq's weapons of mass destruction in Bush's 2002 State of the Union address. Both Bush and Rice said they have the utmost confidence that Hadley can effectively fill Rice's shoes.

The position of national security adviser is not considered Cabinet level and hence does not require Senate confirmation.

Bush said Rice has a big job ahead of her as she takes office at a "critical time" in America's history.

"We're a nation at war, we're leading a large coalition against a determined enemy. We're putting in place new structures and institutions to confront outlaw regimes" and are working to stop nuclear proliferation, bring about peace in the Middle East and break up terror networks, Bush said.

Senate Foreign Relations Committee Chairman Dick Lugar said he would expedite the confirmation process.

"Condoleezza Rice brings extraordinary talents and a gamut of experiences to her new responsibilities as the next Secretary of State," the Indiana senator said in a statement. "I share the strong confidence in Dr. Rice that President Bush has expressed by asking the United States Senate to confirm her promptly."

The Face of the Nation

While Rice is known around the globe, her image does not rival Powell's. The retired four-star general has higher popularity ratings than the president.

"Condoleezza Rice, I think, comes in with some baggage because of both how this Iraq war has gone and also the failure to be more alert before 9/11, so if she is the one and if she is confirmed, she's going to have to build her stature internationally beyond where it is today," said former Michigan Sen. Don Riegle, a Democrat. "It will not be easy following Colin Powell."

Over the next four years, for example, Riegle said the Bush administration needs to focus on a new Mideast policy, as well as the conflicts in Iraq and Afghanistan.

"This job now becomes a much bigger job over this next four years and frankly, the jury's still out," Riegle added.

Rice, 50, worked at the National Security Council (search) in the first President Bush's White House and went on to be provost of Stanford University (search) in California before working on the current president's 2000 campaign.

There had been reports that she intended to return to California or was hoping to replace Donald H. Rumsfeld (search) as defense secretary.

Rice has long been Bush's most trusted foreign-policy adviser, leading to concerns that her elevation to secretary of state might not leave room for dissent within the administration.

"When Rice travels as secretary of state to other capitals, everyone will know that what she says represents with great fidelity what the president thinks" and vice versa, former presidential adviser David Gergen (search) told FOX News.

"I think it does ensure closer cooperation within the administration," Gergen added, but if you "essentially purge the administration" of other voices, that would leave little room for alternative perspectives.

"Colin Powell and his group were often dissenters within the administration, but on some issues they turned out to be right," Gergen continued. He envisioned that Rice would bring in a "hard-line team" of lower-level officials to help her run State.

Added Weinberger: "I think it's a very logical transition and I don't think it's going to be one that causes any problems at all."

The Friction Issue

Gergen also anticipates friction between Rice and the Foreign Service (search), the State Department's elite diplomatic corps, who are considered more liberal than Bush and most of his administration.

"There's a feeling within the Foreign Service that the White House was dumping on, undermining Colin Powell, and he was their hero," Gergen said. A conflict with Rice could cause problems because Foreign Service officers are "the people out there in the field who carry out your orders, are your eyes and ears."

Sen. Jeff Sessions (search), R-Ala., told FOX News he expected Rice to work very closely with Rumsfeld, particularly in the War on Terror and military operations in Iraq.

In his resignation letter dated Nov. 12, Powell, a 35-year Army veteran, decorated general and former chairman of the Joint Chiefs of Staff, told Bush that it was time to "step down ... and return to private life."

He said he would stay on "for a number of weeks, or a month or two" until his replacement was confirmed by the Senate.

"My prediction is, if in fact Dr. Rice is nominated by the president, she will sail through … she will do an outstanding job," said Brad Blakeman, former deputy assistant to Bush.

There had been talk that Deputy Secretary of State Richard Armitage (search), one of Powell's closest friends, might step up to replace his boss.

But word came Tuesday that Armitage gave a letter to Powell on Monday telling him he was also resigning. According to State Department spokesman Tom Casey, it has always been assumed that the two men would leave the agency together.

Gergen speculated that Josh Bolton (search), an agency undersecretary considered a hard-liner, could replace Armitage.

Rumsfeld told reporters Monday he had not yet discussed his own future with the president, praised Powell and said the news media had tried "to fabricate friction" between himself and the secretary of state.

Gergen said that the word as of Monday night was that Rumsfeld would stay on for another two years or so to see through military reforms he has begun, as well as the ongoing war in Iraq.

The Cabinet Shuffle

Also on Monday, the White House announced the resignations of Education Secretary Rod Paige (search), Agriculture Secretary Ann Veneman (search) and Energy Secretary Spencer Abraham (search).

Attorney General John Ashcroft (search) and Commerce Secretary Don Evans (search) resigned earlier. That makes six departures out of 15 Bush Cabinet members. Bush has already picked White House counsel Alberto Gonzales (search) to replace Ashcroft.

Margaret Spellings (search), Bush's domestic-policy adviser, is on the short list to replace Paige.

At least two more resignations are expected.

Tommy Thompson (search), the health and human services chief, likely will be replaced by Medicare chief Mark McClellan (search).

Homeland Security Secretary Tom Ridge (search) has told colleagues he'd probably leave because of personal finances and job stresses. There were reports Tuesday of Ridge's resignation, but that formal action has not yet been taken, a source told FOX News. If he steps down, White House homeland security adviser Frances Townsend (search) is a possible successor.

Other prospects are Asa Hutchinson (search), Homeland Security Department undersecretary for border and transportation security, and former New Jersey Gov. Thomas Kean (search), chairman of the Sept. 11 commission.

One name up in the air is that of John Snow (search), the secretary of the treasury. As of now, Snow is expected to stay on. It will be up to Snow to shepherd through various presidential initiatives such as Social Security reform and tax reform.

Riegle suggested Bush install Cabinet officials who don't all share the same exact views in an effort to "sort of reach across and try to pull the country together."

"I think it would be important to try to create a blended Cabinet," he said.

FOX News' James Rosen and The Associated Press contributed to this report.