By Patricia Zengerle

TAMPA, Florida (Reuters) - Former U.S. Secretary of State Condoleezza Rice brought foreign policy clout to the Republican National Convention on Wednesday, condemning what she described as a stark failure of leadership by President Barack Obama.

In her most significant return to the national stage since leaving the State Department, Rice criticized Obama's handling of uprisings in the Middle East, said the United States has fallen behind China in international trade and has not moved far enough toward energy independence under the Democrat, whom she did not mention by name.

"We cannot be reluctant to lead, and you cannot lead from behind," said Rice, who was greeted with loud cheers by standing, sign-waving delegates.

Rice, the face of foreign policy under Republican President George W. Bush, was part of a lineup of speakers designed to assure Americans that foreign policy would be handled well under Republican presidential nominee Mitt Romney, a former governor of Massachusetts, and his vice presidential running mate, Paul Ryan, a congressman from Wisconsin.

Neither man has extensive international experience.

Romney's attempts to show some clout in foreign affairs have resulted in several stumbles.

He deemed Russia the biggest geopolitical threat America faces, something policy analysts agreed has not been true for years. Romney's critics say that in bashing Obama's record, he has failed to outline his own plans for handling global problems.

Rice also avoided specifics but said the Republican candidates would provide strong leadership.

"Mitt Romney and Paul Ryan will rebuild us at home and they will help us lead abroad. They will provide an answer to the question, 'Where does America stand?'" she said.

Rice largely avoided politics after leaving the State Department in 2009 and has insisted repeatedly that she is not interested in elected office.

But she has played an increasing role in politics this year, campaigning for Romney and other Republican candidates, particularly women.

A rare prominent black woman in a party long viewed as a bastion of white, male power, Rice seemed to be auditioning for something more in her wide-ranging speech, one of the best-received of the Tampa convention.

Rice touted Romney's positions on domestic issues such as education, called for a "compassionate" immigration policy and told her own story - of an African-American girl who grew up in the segregated U.S. South, then became the first black woman to become secretary of state.

"She's a very elegant speaker," said Janice McConaha-Komer, an alternate delegate from Texas. "She certainly is good for us women. She definitely represents women very favorably."

NO MENTION OF AFGHANISTAN

Rice, 57, recently stepped into the spotlight in another way.

On August 20 the Augusta National Golf Club in Georgia, home of the Masters golf tournament, ended an all-male policy that had endured for 80 years by admitting its first two women members, one of them Rice.

The club had admitted its first black member in 1990.

Rice's appearance was a rare reminder during Romney's convention of Bush, the last Republican president, who left office with a 34 percent approval rating. He appeared in Tampa only in a videotaped tribute to his father that was not shown during the convention's prime-time television slot.

Rice was involved in some of the most controversial aspects of Bush's presidency, including the war in Iraq. The only reference to Iraq in her speech was when she cited its struggling new democracy.

She made no mention of the ongoing war in Afghanistan, which began in 2001 when she was Bush's national security adviser but is strongly connected with Obama's greatest foreign policy triumph, the killing of Osama bin Laden in Pakistan.

Ahead of the convention's turn to diplomacy, Romney delivered a scathing criticism of Obama's foreign policy in a speech in Indianapolis on Wednesday.

He accused Obama of weakening America's place in the world, setting the tone for the convention speeches by Rice and another Republican foreign policy heavyweight - Arizona Senator John McCain.

An Obama's campaign spokeswoman lashed back, accusing Romney of using "reckless bluster and vague platitudes" to try to score political points.

In his speech, McCain - who was a prisoner of war during the Vietnam conflict - criticized Obama for the U.S. government's leaks of classified information.

Rice's name emerged in July as a possible vice presidential running mate for Romney, but the speculation faded quickly. Politically, Rice falls to the left of Romney on controversial domestic policy issues such as abortion and gay marriage rights.

(Additional reporting by Deborah Charles; Editing by David Lindsey and Jim Loney)