When President Obama visits China for the first time on Sunday, he will, in many ways, be assuming the role of profligate spender coming to pay his respects to his banker.

That stark fact — China is the largest foreign lender to the United States — has changed the core of the relationship between the United States and the only country with a reasonable chance of challenging its status as the world’s sole superpower.

The result: unlike his immediate predecessors, who publicly pushed and prodded China to follow the Western model and become more open politically and economically, Mr. Obama will be spending less time exhorting Beijing and more time reassuring it.

In a July meeting, Chinese officials asked their American counterparts detailed questions about the health care legislation making its way through Congress. The president’s budget director, Peter R. Orszag, answered most of their questions. But the Chinese were not particularly interested in the public option or universal care for all Americans.