PRESIDENT TRUMP shook the People’s Republic of China in December with his unprecedented phone call with Taiwan’s leader and by suggesting he might alter the one-China policy that has been the bedrock of relations with Beijing for nearly four decades. On Thursday evening, Mr. Trump spoke for the first time during his presidency with President Xi Jinping and pledged to honor the one-China approach. It was a wise turnabout. Now Mr. Trump should get on with a refurbishment of relations with China.

A new study points out those relations are at a “precarious crossroads.” In the past decade, China’s behavior has grown more assertive. It has put muscle into its maritime claims, become more repressive at home and strengthened state control over the economy while protecting Chinese business at the expense of foreign competitors. Overall, say authors of the new task force report, led by Orville Schell of the Asia Society and Susan L. Shirk of the University of California at San Diego, the relationship has become more fraught with risk and more contentious since the 2008 financial crisis.

Mr. Trump has made no secret of his unhappiness with China over trade. But the task force suggests the larger recalibration must be done with care and should focus on six urgent priorities: restraining North Korea’s nuclear and missile programs, reassuring U.S. allies in Asia, righting an imbalance in trade and business relations with China, seeking a rules-based approach to settling maritime disputes, pushing back at China’s repression of civil society and sustaining cooperation on global warming. This is a serious and laudable to-do list.

On North Korea, the group urges Mr. Trump to enlist China actively, setting up a new high-level channel, a shift from President Barack Obama’s approach of “strategic patience.” The group outlines a possible grand bargain in which North Korea agrees to a “verified freeze in the nuclear and missile programs” in exchange for a formal peace treaty replacing the Korean War armistice and diplomatic relations with the United States. If North Korea balks, the United States should impose sanctions on Chinese firms doing business with North Korea and deploy antimissile batteries to South Korea, the report says. That makes sense: A more proactive approach on North Korea is overdue, even if bargaining with Pyongyang is difficult and China’s wholehearted engagement is not assured.

The task force usefully points out that while Chinese think tanks, academic institutions and media are allowed to operate freely in the United States, American nongovernmental organizations are being put under tighter police and government control inside China. Beijing is also curtailing U.S. media and Internet companies. This kind of imbalance should lead the United States to demand more reciprocity from China, the task force says.

As the report makes clear, Mr. Trump is right to want to put the hugely interdependent U.S.-China relationship on a new footing. But it makes no sense to go about slamming doors. The goal should be more openness, reciprocity and rules-based behavior from Beijing.