Cuba's blue, red and white-starred flag was hoisted Monday at the country's embassy in Washington, signalling the start of a new post-Cold War era in U.S.-Cuba relations.

In sweltering heat and humidity, Cuban Foreign Minister Bruno Rodriguez presided over the flag-raising ceremony hours after full diplomatic relations with the United States were restored at the stroke of midnight when an agreement to resume normal ties took effect. Rodriguez later met with U.S. Secretary of State John Kerry, becoming the first Cuban foreign minister to set foot in the State Department since 1958.

"We celebrate this day — July 20 — as a time to start repairing what has been broken and opening what for too long has been closed," Kerry said in Spanish at a joint news conference with Rodriguez. Kerry said he would visit Cuba on Aug. 14 to preside over a flag-raising ceremony at the U.S. Embassy in Havana.

Despite the historic events, there remain issues that continue to vex the U.S.-Cuba relationship.

"This milestone does not signify an end to the many differences that still separate our governments," Kerry said. "But it does reflect the reality that the Cold War ended long ago and that the interests of both countries are better served by engagement than by estrangement."

There remains a deep ideological gulf between the nations and many issues still to resolve. Among them, thorny disputes such as mutual claims for economic reparations, Havana's insistence on an end to the 53-year trade embargo and U.S. calls for Cuba to improve on human rights and democracy. Some U.S. lawmakers, including several prominent Republican presidential candidates, have vowed not to repeal the embargo and have pledged to roll back President Barack Obama's moves on Cuba.

Echoing comments he made at the embassy ceremony, Rodriguez complained anew about the U.S. continuing to retain the Guantanamo Bay Naval Base in Cuba where the American military prison holds terror suspects. And, he repeated demands for the U.S. to end the embargo on Cuba and stay out of Cuba's internal affairs.

"I emphasized that the total lifting of the blockade, the return of illegally occupied territory of Guantanamo as well as full respect for Cuban sovereignty and compensation to our people for human and economic damages are crucial to be able to move toward the normalization of relations," Rodriguez said as Kerry stood beside him.

On a more conciliatory note, Rodriguez thanked Obama for taking steps to ease sanctions thus far and calling on Congress to repeal the embargo.

U.S Cuba diplomatic ties

A tricycle taxi with a U.S. flag is parked on a street in Havana. Cuba is prepared to break with the contentious past, Cuban President Raul Castro said last Wednesday as the two former adversaries restore diplomatic ties. (Reuters)

Rodriguez noted that there are "profound differences" between the U.S. and Cuban governments but stressed that "we strongly believe that we can both cooperate and coexist in a civilized way based on due respect for these differences."

At the Cuban mission earlier, several hundred people gathered on the street outside the embassy, cheering as the Cuban national anthem was played and three Cuban soldiers in dress uniforms stood at the base of the flagpole and raised the flag.

At his remarks inside the embassy, Rodriguez cited Cuban independence leader Jose Marti, who he noted had paid tribute to America's values but also warned of its "excess craving for domination." Cuba was able to survive the past 50 years only because of the "wise leadership of Fidel Castro, the historic leader of the Cuban revolution whose ideas we'll always revere," Rodriguez said.

In Havana, meanwhile, a carnival atmosphere reigned around the new U.S. Embassy overlooking Havana's Malecon seaside promenade. By midmorning, the Cuban government had pulled back several of the eight or so security guards who had stood watch.

Cuba

Cuban supporter Danial Espino Delgado waves a Cuban flag in front of the country's embassy after it reopened for the first time in decades in Washington. (Mark Wilson/Getty Images)

In Washington, some 500 guests, including a 30-member delegation of diplomatic, cultural and other leaders from the Caribbean nation, attended the Cuban ceremony at the stately 16th Street mansion that has been operating as an interests section under the auspices of the Swiss Embassy.

Outside the building, the activist group Code Pink held pink umbrellas that spelled out "Amigos." There were several protesters, including one whose shirt was covered in red paint who was removed from the scene by police.

The United States and Cuba severed diplomatic relations in 1961 and since the 1970s have been represented in each other's capitals by limited-service interests sections. Their conversion to embassies tolled a knell for policy approaches spawned and hardened over the five decades since President John F. Kennedy first tangled with youthful revolutionary Fidel Castro over Soviet expansion in the Americas.

Shortly after midnight, the Cuban Interests Section in Washington switched its Twitter account to say "embassy." In Havana, the U.S. Interests Section uploaded a new profile pictures to its Facebook and Twitter accounts that said US EMBASSY HAVANA. Soon thereafter, the Cuban flag was added in the lobby of the State Department alongside those of other countries with which the U.S. has diplomatic ties.

Members of Congress, both for and against rapprochement with Cuba, were quick to react.

"If we only had embassies in countries whose governments we agree with, we would have to close half of our current embassies, said Senator Patrick Leahy, a supporter. However, New Jersey Senator Bob Menendez, a Democratic opponent, said that "the real goal is a flag raising where the Cuban people are free, have their human rights respected and where we do not accept dictatorial conditions on our embassy and its people."

John Kerry and Bruno Rodriguez

U.S. Secretary of State John Kerry, right, shakes hands with Cuba's Foreign Minister Bruno Rodriguez ahead of a bilateral meeting at the State Department in Washington. (Mandel Ngan/AFP/Getty Images)

Obama has sought engagement with Cuba since he first took office and has progressively loosened restrictions on travel and remittances to the island.

His efforts were frustrated for years by Cuba's imprisonment of U.S. Agency for International Development contractor Alan Gross on espionage charges. But months of secret negotiations led in December to Gross' release, along with a number of political prisoners in Cuba and the remaining members of a Cuban spy ring jailed in the United States. On Dec. 17, Obama and Cuban President Raul Castro announced they would resume full diplomatic relations.

Foreign Affairs Minister Rob Nicholson said Canada was "pleased to have had a role in facilitating the talks that led to the historic announcement" made by Obama and Raul Castro in December.

Canada hosted representatives from both countries as they talked and worked to restore relations.

"We are confident that the re-establishment of diplomatic relations between the United States and Cuba will contribute to the free flow of information, people-to-people ties and improved economic prospects," Nicholson said in a statement.

"Canada will continue working closely with both governments to help build a more prosperous, secure and democratic hemisphere."

With files from The Canadian Press and CBC News