BEIJING » The Chinese government had a special message for President Barack Obama on Thursday: He is black, he admires Abraham Lincoln, so of course he should sympathize with Beijing's effort to prevent Tibet from seceding and sliding back into what it was before its liberation by Chinese troops: a feudalistic, slaveholding society headed by the Dalai Lama.

“;He is a black president, and he understands the slavery abolition movement and Lincoln's major significance for that movement,”; Qin Gang, a Foreign Ministry spokesman, said at a news conference.

Qin added: “;Thus, on this issue we hope that President Obama, more than any other foreign leader, can better, more deeply grasp China's stance on protecting national sovereignty and territorial integrity.”;

For many Americans, Qin's analogy might sound like a stretch, but it revealed which issues Chinese leaders see among their top priorities, ones that Obama will no doubt have to grapple with after he arrives in China on Sunday for his first trip here.

While much attention will be focused on broad international issues like trade and currency values, climate change and the ailing world economy, questions of sovereignty and territory remain an obsession of Chinese foreign policy. Some scholars and analysts see this as an expression of an aggressive expansionism that will only deepen as China moves toward superpower status. Others argue that China is driven more by the need to recover territory wrested from it during the decades it was known as the Sick Man of Asia, when pieces of it were humiliatingly annexed by European powers and Japan.

As a result, Obama can expect to get an earful from Chinese officials not only on the Dalai Lama, whom the president says he will meet after the China trip, but also on Taiwan, the self-governing island that China says is a rebel province. Taiwan receives annual arms shipments from the United States.

“;Tibet and Taiwan are, from China's perspective, the two core sovereignty issues, and they rank above all others in Chinese diplomacy,”; said David Shambaugh, a visiting scholar at the Chinese Academy of Social Sciences.

Disputed territory is also the biggest obstacle in relations between China and its largest neighbor, India. On Tuesday, Qin denounced the Dalai Lama for his visit this week to the Tibetan Buddhist enclave of Tawang in the Indian Himalayan state of Arunachal Pradesh.

Tawang is one of the most potent symbols of China's unresolved sovereignty issues. China says it was once part of Tibet, which the Chinese military seized in 1951, and so belongs to Beijing. India says that Tibetan leaders ceded it to British-ruled India in a 1914 treaty. Tawang figured centrally in a border war between China and India in 1962.

Part of the legitimacy of the Chinese Communist Party lies in the notion, rightly or wrongly held, that it ousted foreign influence from the country and has tried to reunite fragments of China to return the boundaries of the modern nation to roughly those of the Qing Dynasty (1644-1912) at its height. That includes Taiwan, Tibet, the western region of Xinjiang and, by China's calculation, Tawang.

“;In most respects, the People's Republic of China, of course, inherits the fixed boundaries of its predecessor nation-state, the Republic of China, which declared as its territorial boundaries what had been mostly the messy frontiers of the Qing empire,”; Alice Miller, a political scientist and research fellow at the Hoover Institution at Stanford University, wrote in a message posted last week on a China discussion forum.

“;Messy”; is the operative word here. In the age of empires, there were no hard and fast borders, whether the imperial rulers were the Ottoman Turks or the Manchus or the Moghuls. The seat of empire had its sphere of influence, radiating outward, with tributary states occupying the borderlands but rarely being governed in the same way as regions within a modern nation today.

Trying to define national borders along the contours of an old empire is a daunting task. If, for example, Tibet paid tribute to the Qing emperor at certain points in history, should Tibet be part of modern China? If Tawang did the same with Tibetan rulers in Lhasa, should Tawang be part of modern Tibet?

Along with India and Indonesia, China is one of a handful of vast, multiethnic nations that follow the contours of fallen empires. Because of their size and history, all three nations grapple with the same issues: border disputes, ethno-nationalism, occasionally violent movements by disaffected ethnic or religious minorities.

China is often criticized as handling uprisings harshly in Tibet and Xinjiang, which the country's ethnic Han leaders consider internal issues of sovereignty. But in dealing with its neighbors on territorial issues, China has in the recent past generally sought to settle conflicts through negotiation, scholars say.

Since 1949, it has resolved 17 of 23 border disputes, offering concessions in 15 of those instances and, overall, receiving less than half of the contested territory, said M. Taylor Fravel, an associate professor of political science at MIT. The compromises have generally come at times of regime instability, when the Communist Party has felt threatened by external or internal forces, he added.

The big question, then, is whether Chinese leaders will continue to show flexibility on border issues as China becomes a greater world power, and as it stamps out internal threats.

China's maritime disputes have proven harder to settle than those on land. In the resource-rich seas to its east and south, China is trying to assert control of various islands—most notably the Spratly, Paracel and Senkaku or Diaoyu Islands—that are also claimed in whole or in part by other Asian countries. In March, official Chinese news organizations reported that the government intended to send six more patrol vessels to the South China Sea in the next three to five years.

Even the United States has run directly afoul of China's maritime border claims: On March 8, five Chinese vessels harassed an American surveillance ship in what Pentagon officials said are international waters. The Chinese insisted that the American ship, the Impeccable, was conducting illegal surveillance in waters under their jurisdiction.

Dennis C. Blair, the national intelligence director, told Congress that China's general behavior in the South China Sea was “;more military, aggressive, forward-pushing than we saw a couple of years before.”;

This all speaks to how a bolder, brasher China might handle issues of sovereignty and territory, comparisons to Abraham Lincoln notwithstanding.

“;The biggest unknown is how a stronger China will behave in its outstanding disputes,”; Fravel said. “;When it has compromised in the past, mostly in disputes on its land border, it was a relatively weak state. The question now becomes: how will a stronger China behave in its remaining territorial disputes over maritime sovereignty and with India?”;