WASHINGTON - President Barack Obama will open a new era in the United States' thorny relationship with Cuba during a history-making trip with two seemingly dissonant goals: locking in his softer approach while also pushing the island's communist leaders to change their ways.

Obama's visit starting Sunday marks a crowning moment for his ambitious diplomatic experiment with Cuba. After a half-century of acrimony, the two former Cold War foes are now in regular contact.

Joined by his family, Obama will stroll the streets of Old Havana and meet with President Raul Castro. He'll also attend a baseball game and meet with political dissidents.

White House officials say Obama won't gloss over deep, persistent differences. Obama's statements will be closely watched for signs of how aggressively he's pushing on reform and human rights.