Hanoi

Reflecting its buzzing energy, Vietnam is eager to play a larger role in Asia. Given the challenges it faces, America would welcome another willing partner in an increasingly tense region. But the gap between Washington and Hanoi remains large, and unless both sides take the courtship slowly, the chance for a more meaningful relationship may be ruined.

Sitting in a cafe or talking with officials in this city, it's easy to forget this is still a Communist country. Americans used to dealing with traditional allies find a very different reception in Hanoi. Instead of well-trod positions and oft-repeated talking points, officials in Vietnam seem genuinely interested in dialogue. They pepper a visitor with questions, seeking answers to development questions and trying to understand the nuances of American policy.

There is a palpable sense of striving to develop the economy and society. Vietnam's nominal GDP per capita, according to the World Bank, was $1,224 in 2010, which is about a third of the size of China's, but is growing rapidly thanks to nearly 8% growth in GDP over the past decade.

Official trade figures reflect the bustling commerce one sees while walking along Hanoi's streets. While China remains Vietnam's largest trading partner, topping $40 billion in 2011, trade between Vietnam and the United States more than quintupled between 2002 and 2011, from just under $3 billion to over $18.5 billion. The majority of U.S. exports to Vietnam were meat and cars, while Vietnam exported textiles, furniture and fishes. Of that $18 billion in trade, though, America ran an $11 billion trade deficit. This is one reason Washington welcomes Vietnam's participation in the proposed Trans-Pacific Partnership trade negotiations, of which China is not a member.

But Washington's chief interest is strategic. Hanoi has perhaps the prickliest relations with China of any Asian nation. The two fought a border war in 1978 in which both sides claimed victory, and have had running disputes over maritime rights in the South China Sea. China has not only harassed Vietnamese vessels conducting seabed exploration, but has pressured foreign oil companies working with Vietnam to shut down joint ventures in contested waters.

Vietnamese Foreign and Defense Ministry officials are quick to claim that they will not choose sides between Beijing and Washington in what they recognize is a growing competition for influence in Asia. Yet there are numerous indications of wanting closer military ties with the U.S., as long as it can be done quietly. The U.S. Navy held a week-long naval drill with Vietnamese forces in July, just a month after the Vietnamese Navy conducted live-fire exercises in the South China Sea as a warning to China.

As one senior U.S. diplomat told me, "[Washington] can always move forward with Vietnam, but it can never move backward." Vietnamese officials remain leery of getting too close to the Americans, only to find the rug pulled out from underneath them. What the diplomat stressed was that U.S. steps in Vietnam have to be forward-looking, but cautious, since any U.S. retreat from agreements would immediately result in a greater Vietnamese withdrawal.

Another American diplomat noted that there is a broad consensus in the country to do more regionally than just focus on trade. Given that, he suggested Washington needs to focus on Vietnam separately from China, and help its own national goals of improving health care, standards of living and education. That will buy the goodwill necessary to expanding a working relationship on regional issues, including security concerns. Where the two sides remain years apart is on the issue of human rights, especially for dissidents protesting Vietnam's Communist regime and religious protesters.

Overall, one is struck not merely by how welcoming Vietnamese are to Americans, but how little time is spent talking about the Vietnam War. It comes up in discussions, but not as an impediment to exploring closer ties. Nonetheless, the war is ever present in the background and serves as justification for the ubiquitous signs of patriotism in Hanoi, especially the national flag, which seems to be hung from nearly every home and shop.

Given its youth, growth rate and vibrant economic and social life, Vietnam offers greater potential than many other nations in Asia. An America eager for new partners in Asia will have to tread carefully given political differences between Hanoi and Washington, but there seems little question that Vietnam is irrevocably set on a growth path that will make it an ever more important player in Asia over the next generation. Whether this will result in a lasting relationship between two former adversaries remains an open question.

Mr. Auslin is a resident scholar in Asian studies at the American Enterprise Institute and a columnist for WSJ.com.