Secretary of State John Kerry is in Cuba Friday to attend a historic ceremony in which three retired Marines—the same men who took down the American flag in 1961 when the U.S. embassy closed—unfurl the U.S. flag, as the two countries mark yet another chapter in restoring diplomatic relations.

“For more than half a century, U.S.-Cuban relations have been suspended in the amber of Cold War politics,” Kerry said during the ceremony.

He is the first secretary of state to visit Cuba since 1945. The Washington Post outlined the day’s events:

Speeches are to follow the raising of the banner outside the seven-story embassy building, built in the early 1950s on the Malecón, Havana’s sweeping waterfront boulevard. The U.S. Army’s Brass Quintet will play both country’s anthems.

Richard Blanco, who read at President Obama’s inauguration, will read “Matters of the Sea,” a poem he wrote for the occasion. Blanco’s family left Cuba shortly before he was born in 1968.

Last month, the U.S. and Cuba reopened embassies in their respective capitals for the first time since the two countries severed ties more than half a century ago. Kerry, in a news conference at the time with Cuban Foreign Minister Bruno Rodriguez, called the day “historic.” And that it was. The Cuban flag was added in the State Department to those of other countries that have diplomatic relations with the U.S.

Friday’s ceremony in Havana is the latest in a series of actions to reconcile relations between the Cold War-era adversaries. In December 2014, Obama announced the renewal of diplomatic relations with Cuba.

“I applaud President Obama and President Castro for having the courage to bring us together in the face of considerable opposition,” Kerry said on Friday.

Since the announcement, Cuban President Raul Castro and Obama have met face-to-face, and Cuba has been removed from the list of state sponsors of terrorism.

But, while there has been progress, Kerry acknowledged last month the process “may be long and complex.” He added, “Along the way, we are sure to encounter a bump here and there, and moments of frustration. Patience will be required.” The complexity of the process may be evident in Friday’s ceremony. Cuban dissidents, for example, will not be in attendance. As the Associated Press reports:

That presented a quandary for U.S. officials organizing the ceremony on Friday to mark the reopening of the embassy on Havana's historic waterfront. Inviting dissidents would risk a boycott by Cuban officials including those who negotiated with the U.S. after Presidents Barack Obama and Raul Castro declared detente on Dec. 17. Excluding dissidents would certainly provoke fierce criticism from opponents of Obama's new policy, including Cuban-American Republican presidential candidate Marco Rubio.

The reason, according to a State Department briefing on the event:

The opening ceremony, which is the flag-raising ceremony at the embassy, is principally a government-to-government event. It’ll include officials from the Cuban Government, a range of U.S. Government agencies, as well as members of Congress. There will be some U.S. and Cuban private citizens there, but it is primarily a government-to-government event, and it is extremely constrained in space.

The U.S. embargo on Cuba, which can only be lifted by Congress, continues to be a point of contention. In a newspaper column Thursday, former Cuban leader Fidel Castro criticized the embargo’s impact on his country.