The debate about whether to engage China is over — we are now about 20 years into a common-law marriage. The debate about whether China will join the international community also is over. Beijing has been signing up for multilateral forums as if they were going out of style. The great challenge for Secretary of State Hillary Rodham Clinton when she visits Beijing this week is to influence China to play a larger role in preventing global catastrophes in these areas: the economy, nuclear proliferation, climate change and pandemic disease.

China deserves high marks for acting quickly on the global economic crisis. Beijing turned on a dime from trying to cool down its economy last summer to enacting potentially potent stimulus measures over recent months. Some measures, such as a plan to invest $123 billion in universal health insurance over the next three years, could lay the foundation for a social safety net that would help establish a broad Chinese middle class, which would support the growth of the American middle class by fostering a robust market for U.S. exports. Moreover, working with the International Monetary Fund, Beijing is helping to bail out Pakistan, whose economic stability the United States is concerned about, to put it mildly.

The politically challenging issues of currency, intellectual property protection and the potential "Buy American" provisions of the U.S. economic stimulus package remain and could get worse, but they have proved manageable through regular consultation with Congress and steady dialogue with Beijing.

On efforts to prevent potential nuclear catastrophe, China's record is mixed. Beijing is playing an invaluable leadership role in hosting the six-party talks on North Korea's nuclear program and has been instrumental in breaking specific logjams. But Beijing still cares much more about stability on the Korean peninsula than it does about North Korea's nukes (which are not aimed at China, after all). Whether and under what conditions Pyongyang would give up its weapons, and how much arm-twisting China would be willing to do, are unclear. Clinton is sure to make a strong pitch for more Chinese pressure, but here Beijing and Washington have at least agreed on a path forward.

In contrast, on nuclear catastrophe scenario No. 2 — Iran's program — China and the United States sharply diverge. China repeatedly has blocked U.S. efforts in the U.N. Security Council to impose tough sanctions on Tehran. Beijing does not want to see a Middle East made even more dangerous by complicated nuclear dynamics, but China's immediate and pressing lust for energy supplies will leave its anti-proliferation policies compromised at best. Prospects for Clinton to make headway on this issue seem dim.

That brings us to climate change. Global warming will demand the most creative and intense diplomacy the Obama team has to offer. China's energy demand is mind-blowing in scale. From 2001 through 2007, China's consumption increased by an amount equal to energy use in all of Latin America, according to Asia energy expert Mikkal Herberg.

China is firmly opposed to hard targets for reducing its ballooning greenhouse-gas emissions, arguing, with reason, that the West caused the global warming crisis and bears the burden of responsibility. But without China on board, the world will not be able to reduce greenhouse gases to the level that scientists think is necessary to avoid catastrophic effects.

You know things are bad when avian flu seems like a bright spot. But there's reason for guarded optimism that China will handle outbreaks responsibly: A Chinese doctor heads the World Health Organization, more money is headed for rural healthcare in China, and Beijing learned from the SARS crisis earlier this decade that the potentially devastating effect of a pandemic is exacerbated when its early cases are covered up.

What tack, then, should Clinton take in her first trip abroad as secretary of state to maximize the chances of progress in preventing these global catastrophes?

First, while making plain our differences (on human rights, China's military buildup, currency, Darfur, Tibet and other issues), she should make clear that China is a strategic partner in crucial areas and that the United States welcomes China's integration into the international system as a responsible, respected and engaged stakeholder.

She also should pave the way for new, bold initiatives based on "strategic collaboration." One potentially fruitful area is clean-energy research, with the United States and China, or a group of the major energy consumers, joining forces.

In her confirmation hearing, Clinton indicated that in dealing with other nations she would maintain her focus on the entire relationship and not allow single issues to set the tone and direction. That is the right approach, but that does not prevent her from prioritizing U.S. interests around these four challenges in her talks in Beijing. It is in the nature of our deeply interdependent relationship to have a long list of issues that we want action on from China, but we are likely to see more progress if we can be clear about which are most important.