(Adds announcement of new U.S. measures in paragraphs 3, 23-24)
By Matt Spetalnick, Jeff Mason and Patricia Zengerle
WASHINGTON, March 15 (Reuters) - Barack Obama's historic visit to Havana next week may be the closest he comes to a Nixon-goes-to-China moment, but he also has another more practical goal: to make his opening to Cuba irreversible for the next U.S. president.
The Obama administration hopes that getting more U.S. companies invested in Cuba and loosening up travel to the island will make it almost impossible for traditionally pro-business Republicans to halt or even roll back the thaw in relations if they win the White House in November.
Ahead of Obama's March 20-22 trip to Havana, his administration rolled out sweeping new measures on Tuesday to make it far easier for Americans to visit the island and do business there. The stage has also been set for a string of business announcements from the hotel and telecommunications industries and possibly even Major League Baseball.
"The administration wants to do as much as it can unilaterally before the clock runs out," said a person who has been briefed on Obama's strategy.
What remains to be seen, however, is whether Obama can prod Cuba's prickly Communist government to reciprocate, at least with modest economic reforms that would help ensure his policy sticks.
Cuba's leaders have been slow to loosen their grip on the island's state-run economy. That plus strict limits that remain under the U.S. economic embargo against Cuba has made many American firms wary.
Obama's critics accuse him of giving up too much in return for too little from Cuban President Raul Castro and now taking a premature "victory lap."
But administration officials say deeper U.S. engagement should not be contingent on concessions from the former Cold War foe, such as improving its human rights record.
Obama and his advisers insist that his outreach to Havana has a better chance of sowing the seeds of eventual change than what they see as a failed U.S. policy of isolation pursued for more than half a century.
"This is not a matter of providing concessions," Obama told CNN en Espanol. "This is a matter of us engaging directly with the Cuban people."
Obama's visit - the first by a U.S. president in 88 years - is meant to showcase that approach.
But it is also a gamble for a U.S. leader whose strategy of engaging adversaries has had mixed results. Locking in his Cuba opening would make it a major piece of his legacy.
Obama has relied on executive powers to jump-start the normalization of ties given continued resistance in Congress to lifting the longstanding U.S. embargo. His challenge is to advance the process to the point that no successor could unravel it.
Cuba has not figured heavily in the 2016 presidential race but it could emerge, especially in Florida, a swing state and home to the largest Cuban-American community. For decades, Cuban-Americans were broadly opposed to any rapprochement but a younger generation has warmed to Obama's policy shift.
Democratic candidates Hillary Clinton and Bernie Sanders have pledged to stick with Obama's opening to Cuba if elected.
Republican front-runner Donald Trump said last week the old policy needed to be changed but he would renegotiate with Cuba for a better deal. His closest challengers, Ted Cruz and Marco Rubio, both Cuban-Americans, said they would reverse Obama's approach altogether.
Despite that, Obama told CNN en Espanol he believes Congress will remove the embargo in the next administration, whether led by a Democrat or a Republican - though he acknowledged there were not yet enough votes.
It would be hard for many Republicans to join in overturning Obama's measures if the White House succeeds in green-lighting enough corporate projects in Cuba, congressional aides said.
AT&T Inc, Starwood Hotels & Resorts Worldwide Inc and Marriott International Inc are expected to sign deals around the time of Obama's visit.
Most companies remain cautious, however, because of Cuba's dual-currency system, rigid labor market and opaque legal system.
"There are still some frustrations," said James Williams, president of Engage Cuba, a pro-trade lobbying group. "But they are not insurmountable."
Some concerns may be eased with Washington's move on Tuesday to relax limits on the use of dollars in Cuba transactions, removing a big obstacle to Havana's access to the global banking system.
U.S. airlines have already rushed to apply for routes to the island, and new travel rules announced on Tuesday will make it easier for Americans to travel to Cuba independently rather than in group tours. That in turn could boost public support for normal relations.
Ben Rhodes, an Obama adviser who helped secure the breakthrough with Cuba in December 2014, said the administration has told Cuban leaders the impact of U.S. regulatory changes will be limited unless they do more to reform their economy.
U.S. officials will pay close attention to Cuba's Communist Party Congress, set to convene in April for the first time since 2011.
Still, they acknowledge that the prospects remain dim for influencing democratic reform, even though Obama plans to meet dissidents in Havana.
"We don't view our steps as the types of things that would cause the Cuban government to change their political system," Rhodes told Reuters.
Communist Party newspaper Granma last week said Cuba would not renounce its "revolutionary and anti-imperialist ideals."
Some of Obama's critics say the visit itself is validation of dictatorial rule.
"The only thing that's changed as a result of this opening is that now the Cuban government has more sources of money from which to build out their repressive apparatus," Rubio said in a Republican debate last week. (Additional reporting by Daniel Trotta in Havana; Editing by Kieran Murray and Frances Kerry)