After more than five decades, the U.S. embassy in Cuba formally re-opened with a flag-raising ceremony on Friday, marking another historic step in the normalization of relations between the two countries.

“For more than half a century, U.S.-Cuba relations have been suspended in the amber of cold war politics,” Secretary of State John Kerry said in a speech at the seaside facility. “It’s time to unfurl our flags and let the world know we wish each other well.”

Kerry spoke, occasionally in Spanish, on a podium outside the embassy, moments before U.S. Marines raised the American flag there for the first time in 54 years. The Cuban embassy in Washington, D.C. re-opened in July.

But however landmark the event, tensions remain. The U.S. economic embargo against Cuba is still in place and the U.S. prison at Guantanamo Bay remains open.

As global affairs correspondent Elise Labott wrote for CNN on Friday, “signs of mistrust linger, and beyond the pomp and circumstance lies a long road back from more than half a century of diplomatic animosity.”

On Thursday, which also happened to be his 89th birthday, former Cuban leader Fidel Castro called for the U.S. to repay millions of dollars owed to his country for damage done by its decades-long embargo—an embargo many on Capitol Hill are saying should end.

“The rhetoric from the leader of the Cuban revolution, and the face of anti-U.S. resistance, is not unexpected,” Labott wrote. “But it underscores the long-standing tensions at play as Washington and Havana work to thaw the decades-long chill in relations.”