Defense Secretary Donald H. Rumsfeld will make his first official trip to Beijing next week to hold a "straightforward exchange" on strategic concerns -- including China's military buildup -- and make an unprecedented visit to the headquarters of China's nuclear forces, senior defense officials said yesterday.

While underscoring Washington's suspicions about China's aggressive military modernization, the officials said Rumsfeld's trip marks an opportunity for improving U.S.-China military ties four years after they ruptured over the collision off China's coast of a U.S. Navy spy plane and Chinese fighter jet.

"We have serious strategic interests which don't always coincide but . . . Secretary Rumsfeld goes there with the intention of having some positive outcome," said one senior defense official briefing reporters about the trip, which begins Monday. He spoke on the condition of anonymity.

In-depth talks between Rumsfeld and Chinese military and Communist Party leaders -- as well as signs of Beijing's willingness to disclose more about its growing military capabilities -- could advance a relationship that a number of U.S. officials said was on a good, upward trajectory.

China, for its part, has actively sought the visit by Rumsfeld for four years -- largely for symbolic reasons, defense officials and China analysts say. "The Chinese military wants this visit far more than the American military. Rumsfeld's reluctance to go to China is legendary," said one expert on Chinese security issues who spoke on the condition of anonymity because of the sensitivity of the trip.

Beijing seeks to demonstrate, by hosting a perceived Bush administration hardliner, that Washington is not shunning China as a looming military foe, they say. "China will probe for signals from Rumsfeld and DOD [Department of Defense] on the extent to which the U.S. views China as a major regional security threat," said Evan Medeiros, a China military expert at the Rand Corporation here.

Chu Maoming, spokesman for the Chinese Embassy in Washington, said: "The visit is imperative and helpful to promote mutual understanding, enhance mutual trust, and also expand exchanges."

One of the most striking signs of Beijing's desire to woo Rumsfeld is its agreement to allow a U.S. delegation for the first time to visit the headquarters of China's most secretive military command, the Second Artillery Corps, which oversees the nation's arsenal of conventional and nuclear missiles.

"We are pleased that they accepted this particular request," said a senior Pentagon official. "We hope that by going there and meeting with the commander of Second Artillery . . . that we will have an opportunity to receive a deeper and more detailed briefing."

Agreeing to the long-standing U.S. request to visit the facility, at Qinghe outside Beijing, signals "a new precedent of transparency on the Chinese part, but we'll have to see what the Chinese show us," said Peter Brookes, a Heritage Foundation analyst and former defense official involved with China policy in the first Bush term. "Is it substantive or a dog-and-pony show?"

In contrast, Beijing rejected a long-standing U.S. request to visit what some defense officials call the "real Chinese Pentagon" -- a command center in the Western Hills outside the capital. "That was not granted to us," a Pentagon official said. Nor has China yet accepted a U.S. proposal to establish a telephone hotline between the U.S. and Chinese militaries as a confidence-building measure, he said.

Indeed, Pentagon officials said that while they will discuss expanded high-level visits, educational exchanges and naval port calls, they expected no major breakthroughs or agreements with China. "Our thought is that this will be a non-euphoric encounter," one senior defense official said.

Rumsfeld's itinerary appeared designed to tone down the trip: He will make no major speech in China -- a deliberate decision, officials said -- holding round-table sessions instead. And rather than an exclusive visit, China will be just one leg of a far-flung Asian tour that will also take the secretary to South Korea, Mongolia, Kazakhstan and Lithuania.