Fidel Castro's leaving office on his own terms is not the kind of change that successive American presidents have envisioned for Cuba. In fact, it's a sign that U.S. efforts to isolate that country and bring down its socialist government have failed.

Today Venezuela, China, Canada, Spain and Brazil all have a robust presence on the island. Venezuela continues to trade cut-rate oil for Cuban doctors.

Canada, Spain and China have made major investments in Cuba over the past decade in tourism, nickel and energy.

These relationships helped enable Cuba to achieve 7 percent economic growth last year (a CIA estimate) in spite of U.S. efforts to limit hard-currency flows to the island.

As interim leader, Fidel's brother Raul has spotlighted longstanding economic problems, criticized the government's performance and raised expectations of policy changes that will improve conditions for the average Cuban.

Regardless of whether Cuba's next president delivers or disappoints, Cuba is on the verge of generational change as Fidel Castro and his cohorts leave the scene, one by one. America's next president faces a choice: Continue a Cuba policy rooted in ineffective sanctions or tailor U.S. policy to new possibilities.

Some countries friendly to the United States are already moving ahead. Spain has begun a human rights dialogue with Cuba.

Brazilian President Luiz Inacio Lula da Silva, who recently offered Cuba a $1 billion line of credit, offers the island a possible alternative to its dependence on Venezuelan President Hugo Chavez.

Treating Cuba as an all-or-nothing proposition has netted the United States nothing. Our interests go unserved and our ideals unmet.

There are many steps the next American president can take to increase our influence in Cuba. Whether or not a Cuban successor government schedules multiparty elections and releases all political prisoners (unlikely in the near future), the next U.S. president has security interests to protect: stemming the flow of illegal immigrants, enhancing security around the U.S. base at Guantanamo, stopping U.S.-bound drug-runners transiting Cuban waters, and protecting against environmental damage to Florida's coast by foreign oil exploration in Cuban waters.

Dialogue on these security issues could yield direct results and also build contacts and confidence that might put the next U.S. administration in a position to more effectively advance other pressing interests.

These include political, labor and human rights in Cuba, settlement of U.S. claims there, and, eventually, negotiation of trade and regulatory regimes that will put American business interests in Cuba back on an equal footing with foreign competitors.

U.S. restrictions on travel to the island have failed to tangibly weaken the Cuban government, even as they have contributed to the increased isolation of the Cuban people.

Contact between our societies ought to be encouraged. At a minimum, the next president should permit the kind of people-to-people exchanges - involving artists, musicians, academics, students, religious groups and others - that President Reagan embraced with the Soviet Union in the 1980s. Programs of this kind flourished with Cuba until 2003, allowing Cubans from all walks of life to exchange ideas and information with American counterparts.

The Bush administration's 2004 sanctions targeting visits and remittances by Cuban Americans should also be reversed. The contacts and the financial help are important lifelines to Cubans, many of whom are struggling to make ends meet.

The next U.S. administration should also consider talks on loosening the restrictions that keep U.S. and Cuban diplomats confined, for the most part, to the capitals in which they are posted. An agreement in this area would allow our diplomats to gain the insights and influence in Cuba that current policy denies them.

America's next president should harbor no illusions that modest policy adjustments will lead directly to the political and economic outcomes we seek in Cuba. But they would serve American interests and, if pragmatism eventually prevails in Cuba, help advance the interests of the Cuban people as well.

The writer is a senior fellow with the Lexington Institute.