* U.S. negotiators call talks "fruitful"
* Focus on pilot project for mail delivery
* Tour of Cuban mail facilities for U.S. delegation (Recasts, adds statements, U.S. to tour mail facilities on Tuesday)
By Marc Frank
HAVANA, Sept 16 The United States and Cuba concluded on Monday their second round of talks aimed at re-establishing direct mail service between the two countries after a 50-year ban, but left for later the most sensitive issue - Cuban planes landing on U.S. soil.
The Cuban Foreign Ministry said both sides had agreed to continue the talks in the near future and that it had emphasized, "working out the transportation of mail by regular direct routes in both directions," was key to their successful conclusion.
The State Department said something very similar in a statement: "The goal of the talks is for the United States and Cuba to work out the details for a pilot program to directly transport mail between the two countries."
Cuba said talks between the postal services of the two countries took place "in a respectful manner," and the U.S. Interests Section said U.S. officials "described the discussions as fruitful."
The U.S. delegation, led by U.S. postal service executive director for international postal services, Lea Emerson, was to tour Cuban mail facilities on Tuesday, the U.S. Interests Section said.
The two countries do not have diplomatic relations, but maintain lower-level missions in each other's capitals.
Direct mail service between the United States and Cuba has been suspended since 1963. Despite the ban, letters and other mail still flow between the United States and the island nation 90 miles away through other countries, such as Canada, Mexico and Panama.
Relations between the two countries have been frozen since soon after Cuba's 1959 revolution led by Fidel Castro, and Washington has maintained economic sanctions on Cuba for more than half a century.
Monday's talks took place amid a few signs the Obama administration and President Raul Castro have not completely given up on some improvement in the two countries' hostile standoff.
Former British ambassador to Cuba, Paul Webster Hare, who lectures on international relations at Boston University, said Cuba's decision not to allow fugitive former U.S. intelligence analyst Edward Snowden to fly from Russia to Cuba on the way to exile in Latin America, was significant.
"The Cubans recognized that for any prospect of better relations they needed to avoid more long-term irritants," he said.
ON AGAIN, OFF AGAIN
Obama restarted immigration and postal talks with Cuba in 2009, both were suspended by the Bush administration in 2004.
The separate talks were also seen at the time as a sign of further thawing in U.S.-Cuba relations under Obama, who had earlier relaxed restrictions on remittances and travel to the island for Cuban Americans.
Both the postal talks and immigration talks were suspended again soon after the arrest in December 2009 of U.S. contractor Alan Gross, sentenced in 2011 to 15 years for his role in setting up an underground Internet network in the Communist-run country.
Cuba has hinted at a possible swap of Gross for four Cuban agents arrested 15 years ago and still being held in the United States on espionage convictions.
Cuba allowed a U.S. doctor to visit Gross in August, something it had refused to do in the past.
A significant improvement in U.S.-Cuba relations must include the release of Gross and the Cuban agents, according to some analysts, while others said progress on secondary issues could lead to more significant change.
"Their release may ultimately come from a process of improving relations between Cuba and the U.S., where both nations engage in a progressive tit for tat," said Carlos Saladrigas, a Cuban American businessman who advocates engagement with Havana and heads the Cuba Study Group.
"Politically it is easier to conceive of their release as a consequence of a process than as the trigger," he said. (Additional reporting by Nelson Acosta; editing by Andrew Hay and Jackie Frank)