Defense Secretary Leon Panetta, right, and his Japanese counterpart Satoshi Morimoto leave after their joint press conference at Defense Ministry in Tokyo Monday, Sept. 17, 2012. Panetta says that U.S. and Japanese officials have agreed to put a second missile defense system in Japan. (Shizuo Kambayashi/AP)

Defense Secretary Leon E. Panetta has been promised an audience with Chinese Vice President Xi Jinping, U.S. defense officials said Monday, in what would be the Chinese leader’s first meeting with a foreign leader since he mysteriously vanished from view this month.

U.S. defense officials said the Chinese government confirmed that Xi would meet Wednesday with Panetta in Beijing’s Great Hall of the People, apparently in an emphatic bid to dispel doubts about the Chinese leader’s health and political future.

Xi canceled meetings with Secretary of State Hillary Rodham Clinton and other foreign dignitaries without official explanation this month, fueling rumors about his status as China’s putative leader-in-waiting. He reappeared in public briefly Saturday during a visit to a Chinese university.

Speculation arose that he had been sidelined by a bad back or a bad heart at a time when China is preparing for a major once-in-a-decade leadership transition. Xi is expected to be named as China’s new president in coming weeks. Chinese authorities said Sunday that Xi would also appear at an expo attended by Southeast Asian leaders later this week.

Panetta arrived in Beijing on Monday for his first visit to China since taking over as Pentagon chief in July 2011. He was originally scheduled to spend two days in the country, but U.S. defense officials announced that he would extend his visit to a third day.

In addition to meeting Xi, Panetta is scheduled to visit a People’s Liberation Army naval base, give a speech to Chinese cadets and tour a submarine and frigate.

His arrival in China comes at a time of heightened security tensions in the region, as well as an ongoing effort by the Obama administration to reassert its strategic interests in Asia.

Earlier Monday, for example, the United States and Japan announced they will expand a shared missile defense system in East Asia by installing a new, high-powered radar in southern Japan.

During a joint news conference in Tokyo, Panetta and Japanese Defense Minister Satoshi Morimoto said a joint U.S.-Japanese team would begin searching immediately for a site for the new radar, which would bolster one already in place in northern Japan, on the island of Hongshu.

U.S. and Japanese leaders say the missile shield is intended to defend against the threat of an attack by North Korea, which has developed a small arsenal of nuclear weapons and is seeking to extend the range of its long-range missiles so they could reach U.S. territory.

Although Washington and Tokyo have repeatedly denied that the missile defenses are designed to counter China, the developments have heightened suspicions in Beijing that a secondary aim of the program is to contain China’s growing military power in the region.

Panetta told reporters that there was no reason for the Chinese to think the radar would target them.

“It’s no secret that one of our concerns in this area is the ballistic missile threat from North Korea,” he said. “We have made these concerns very clear to the Chinese. We’ve also made clear that we’ll take steps to protect the United States and our allies from that threat.”

U.S. officials said the second land-based radar in Japan would enhance their ability to detect a North Korean missile launch. The U.S. and Japanese navies operate similar radars from aboard cruisers and destroyers that patrol east Asian waters on a regular basis.

“The purpose of this is to enhance our ability to defend Japan,” Panetta added, referring to the land-based radar. “It will also be effective in protecting the U.S. homeland from the North Korean ballistic missile threat.”

In addition to detecting ballistic missiles, however, the radars also provide the U.S. military and its allies a highly detailed view of ship traffic in the region. That capability is particularly desired by U.S. allies in the region that are engaged in territorial disputes with China over contested islands and fishing grounds.

For instance, officials in the Philippines have asked the Obama administration to consider placing a similar land-based radar on their territory to gather intelligence on maritime traffic in the South China Sea. The Philippines and several other countries in the region have been butting heads with China over control of the mineral-rich seabed and local shipping lanes, which are some of the busiest in the world.

In addition to radars, the U.S. military has been expanding its use of surveillance drones in Asia across the wide expanses of the Pacific Ocean, relying primarily on unarmed, high-altitude Global Hawk aircraft.

Japan has expressed interest in obtaining Global Hawks or other surveillance drones. Morimoto alluded to this in a joint news conference with Panetta in Tokyo, saying the two countries are “deepening cooperation on surveillance and reconnaissance activities.”

The agreement to deploy a second land-based radar in Japan was announced hours before Panetta was scheduled to arrive in Beijing.

The radar deal also comes amid a worsening dispute between Japan and China over the disputed rights to a collection of uninhabited islands in the East China Sea. Massive anti-Japanese demonstrations have erupted across China in recent days to protest the Japanese government’s recent decision to purchase the islands from a private Japanese landowner. The islands are known as the Senkaku in Japan and Diaoyu in China.

The Pentagon has been seeking to improve military relations with the People’s Liberation Army. Beijing, however, has been leery of the overtures, and many PLA commanders have accused Washington of seeking to contain its growing military and economic influence in Asia and the Pacific.