By Tim Johnson, McClatchy Foreign Staff (TNS)

PANAMA CITY — The thaw in the lengthy diplomatic freeze between the United States and Cuba quickened Friday, with President Barack Obama and Cuban leader Raul Castro shaking hands at an evening reception ahead of a more substantive face-to-face meeting set for Saturday.

The two leaders’ greeting included no other significant interaction or substantive conversation, a White House official said. But it was closely watched as the first time Obama and Castro have encountered one another since they announced in December that their two countries were working to re-establish diplomatic relations severed in 1961.

U.S. National Security Council spokeswoman Bernadette Meehan said in a one-sentence statement that the two leaders “greeted each other and shook hands.” Photos showed Obama facing Castro, who was accompanied by Cuban Foreign Minister Bruno Rodriguez.

The handshake capped what Ben Rhodes, the White House deputy national security adviser, had described earlier as a ratcheting up of contacts between the two countries’ officials that would have been “unimaginable a year ago.”

Rhodes said Obama and Castro had talked earlier in the week by phone, disclosing a previously unannounced conversation. In addition, Secretary of State John Kerry and Foreign Minister Rodriguez held a lengthy meeting late Thursday night that was billed as the highest-level meeting between U.S. and Cuban officials in nearly six decades — a distinction it will lose when Obama and Castro hold their one-on-one discussion “on the margins” of the Summit of the Americas on Saturday.

“We’ve already had the first interaction, the first meeting, between our foreign ministers since 1958. That happened last night. We’ve had the first phone calls between the president of the United States and the president of Cuba that I’m aware of since a similar time frame,” Rhodes said.

“We’re in new territory here.”

Rhodes said Kerry and Rodriguez discussed “very practical, specific, and sometimes technical issues” related to restoring embassies in their respective countries.

Asked if Washington wants the government of Cuba, ruled by either Fidel Castro or his brother Raul since 1959, to be toppled, Rhodes dismissed the suggestion.

“We’re not focused on overthrowing the Cuban government. We’re not focused on changing the existing regime at a time when we’re engaging that government,” he said.

The phone conversation between Obama and Raul Castro on Wednesday was not particularly long, Rhodes said, while Kerry’s contact with his counterpart was broader and deeper.

The United States severed diplomatic ties with Cuba in 1961 following the Cuban Revolution, which sent hundreds of thousands of Cubans into exile, setting off a tense relationship that has become a major factor in both U.S. domestic politics and international tensions. Cuban-Americans are an influential voting bloc in battle-state Florida, and the U.S.-Cuba rivalry has had repercussions for decades, from the Western Hemisphere to Africa.

Obama and Castro have shaken hands before, in 2013 at the memorial service for the late South African leader Nelson Mandela. But while that one was the first such courteous gesture in half a century between the country’s leaders, Friday night’s hand clasping of hands seemed to portend even more momentous changes in a relationship that has split not just the two countries, but the Western Hemisphere. Until this year, no Cuban leader had been invited to a Summit of the Americas, a gathering of all the Western Hemisphere nations, since the event was initiated in 1994.

Vestiges of the strained relationship were on display in the early afternoon as Cuban dissidents and their supporters clashed with backers of the Castro government outside a Panama City hotel in a second day of violence.

Protesters pushed, shoved and shouted at one another outside the Hotel Panama, a luxury hotel in the city’s banking district where a forum was being held to bring together civil society leaders from across the Americas. Many waved Cuban flags. Panama’s main television network called for police to restore order.

Cuba was not the only source of tension. Venezuelan leader Nicolas Maduro arrived in Panama in the afternoon and headed directly to the working-class neighborhood of El Chorrillo, where he laid a wreath at a monument in honor of Panamanians who died resisting the 1989 U.S. invasion that toppled then-dictator Manuel Noriega. Bombing during the invasion heavily damaged high-rises in El Chorrillo.

At midmorning, with temperatures already soaring to the high 80s, Obama toured the Miraflores Locks on the Pacific side of the Panama Canal, itself a reminder of the United States’ long, sometimes acrimonious relationship with Latin America. Wearing sunglasses, Obama climbed the control tower that oversees movement of vessels, then walked along a narrow pedestrian walkway that traverses the locks chambers.
Secret Service agents were aboard vessels nearby as Obama crossed the canal.

Between 12,000 and 14,000 ships transit each year between the Atlantic and Pacific oceans through the canal, which was controlled by the United States until the 1970s, when a treaty surrendered jurisdiction to Panama.

Later, Obama said he “saw the extraordinary progress that is being made” on a $5.2 billion project to expand the canal, scheduled to conclude early next year.

“It really is a symbol of human ingenuity but also Panama’s central role in bridging two continents and bringing the hemisphere together,” Obama said.

Panama held out hope that the summit, which concludes late Saturday afternoon, would not only showcase the rapprochement between Cuba and the United States but help mend tense U.S. relations with Venezuela.

“Where there are differences, let us create bridges,” said Martin Torrijos, a leftist former president of Panama.

Torrijos recalled Panama’s history as a facilitator of peace talks in the 1980s aimed at ending wars in Central America and said, “I hope this can repeat itself.”

(c)2015 McClatchy Washington Bureau, Distributed by Tribune Content Agency, LLC

Photo: Day Donaldson via Flickr