T

he highest-level US delegation to Cuba in decades kicked off two days of negotiations Wednesday after grand promises by President Barack Obama about change on the island and a somber warning from Cuba to abandon hopes of reforming the communist government.

US moves to restore diplomatic relations with Cuba and loosen the five-decade trade embargo have '€œthe potential to end a legacy of mistrust in our hemisphere'€ and have '€œadded up to new hope for the future in Cuba'€, Obama said in his State of the Union address Tuesday night.

A senior Cuban official cautioned, however, that restoring diplomatic ties with the US would not immediately lead to a full relationship between the Cold War foes after a half-century of enmity.

The message appeared designed to lower expectations, coming just before Obama spoke to a Capitol audience that included Alan Gross, whose release from Cuba in a prisoner exchange last month cleared the way for a new relationship.

Wednesday'€™s conversations in Havana started with a continuation of efforts by the two sides in recent years to promote what the State Department calls '€œsafe, legal and orderly migration,'€ covering everything from the security of charter flights that travel regularly between Miami and Havana to rooting out fraudulent passports and partnering on potential search-and-rescue missions.

Thursday'€™s talks are trickier, scheduled to deal with the mechanics of re-establishing a US Embassy in Havana headed by an ambassador, and a Cuban Embassy in Washington.

Last month'€™s announcement of detente has spawned high optimism on both sides of the Florida Straits, but the high-ranking Cuban diplomat said Cuba '€œisn'€™t normalizing relations with the United States'€. He said Cuba was re-establishing diplomatic ties, but the process of normalization is '€œmuch longer and deeper'€. Reporters were briefed on condition that the official not be quoted by name.

Republican leaders in the House and Senate are opposed to rapidly rebuilding the relationship as long as President Raul Castro remains firmly in control of Cuba. Other obstacles include billions of dollars in economic claims against Cuba'€™s government, American fugitives living freely in Cuba and the opposition of many Cuban-Americans.

Still, the biggest potential challenge is Castro'€™s government itself, which needs cash for its stagnant economy but fears Obama'€™s new policy merely repackages the longstanding US goal to push him from power.

The Cuban diplomat expressed optimism about the long-term prospects for US-Cuban relations as long as Washington does not try to change Cuba'€™s single-party government and centrally planned economy '€” tenets of Cuba'€™s system the US has long opposed.

American officials have repeatedly said they hope their new path of engagement will empower Cubans and soften the government'€™s control over the country.