China's future leader appeared energetic Wednesday in a meeting with the U.S. defense secretary, his first appearance with a foreign dignitary since dropping from public view and raising a flurry of questions about his health and turbulence in the succession process.

Vice President Xi Jinping and Defense Secretary Leon Panetta met for more than an hour to discuss U.S.-China military relations, Pentagon press secretary George Little said.

Panetta said the meeting went over the allotted 45 minutes because Xi was so focused on finding a way to improve relations.

"Frankly my impression was that he was very healthy and very engaged," he told reporters later in the day.

Video of the meeting shot by state broadcaster CCTV showed a robust-looking Xi shaking Panetta's hand, posing for photos and smiling during their conversation. The report made no mention of Xi's absence or any health issues.

While Panetta's visit comes at a sensitive time for China and its relations with the U.S. and regional neighbors, his meeting with Xi was closely scrutinized for any clues about the vice president's prolonged absence, which ended Saturday when he appeared at an event for national science promotion day.

In addition to being China's vice president, Xi is also a vice chairman of the Central Military Commission that oversees the 2.3 million-member People's Liberation Army, and is due to take over as head of the ruling Communist Party later this year and as president in the spring.

In keeping with its secretive one-party political system, Beijing has offered not a shred of information about why Xi was not seen in public, triggering speculation he had injured his back or suffered a heart attack or stroke. Some had questioned whether he had fallen foul of President Hu Jintao or other top leaders, reflecting continuing uncertainty surrounding the succession and lingering political fallout from the downfall of a charismatic leader, Bo Xilai.

China has not even announced dates for the congress that will install Xi and other top leaders, an event held every five years that last time began in mid-October. That has led to speculation that the party has yet to agree on the makeup of the all-powerful Politburo Standing Committee or even whether to reduce it in size from nine to seven seats.

Other crucial matters also remain up in the air, including what if any political reforms to embark on amid a rapidly slowing economy and growing social unrest. More than ever, finding common ground among the party's various constituencies appears to be a daunting task.

"The delay apparently does suggest anything but a smooth transition of power, namely, the extraordinary difficulty of reaching consensus on the composition of the Politburo, including the Standing Committee, as well as how to handle factional politics that has never been so acute," said Warren Sun, a China expert at Australia's Monash University.

The party has also yet to announce how it plans to handle the still-popular Bo, whose wife Gu Kailai was convicted last month of murdering a British businessman and whose former police chief and top lieutenant Wang Lijun was tried this week on charges including bribery and attempting to defect to the U.S.

Bo is widely expected to face an eventual trial, although it isn't known on what charges, and he remains under party investigation for unspecified grave violations of discipline. Harsh punishment could spark a backlash from supporters in the party, the military and among the public, while failure to discipline Bo would underscore weakness in the legal system and among the leadership.

Xi is facing "enormous hurdles to establish a highly unified leadership team," Sun said.