Cuba's blue, red and white-starred flag was hoisted Monday at the country's embassy in Washington, signaling 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. Earlier, without ceremony, 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. U.S. and Cuban diplomats in Washington and Havana also noted the upgrade in social media posts.

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.

But there were also signs of the sore points that continue in the U.S.-Cuba relationship. In 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.

He also slammed the U.S. for continuing to hold on to Guantanamo Bay, the U.S. naval base in Cuba where the American military prison continues to hold terror suspects. Rodriguez said Guantanamo was a "nefarious consequence" of U.S. attempts to dominate the hemisphere.

"Only the lifting of the economic and commercial and financial blockade which has caused so much harm and suffering to our people, the return of occupied territory at Guantanamo and the respect for Cuban sovereignty will lend some meaning to this historic event to which we bear witness today," Rodriguez said, repeating demands the Cuban leaders have made throughout the normalization process.

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

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.

A pair of officers stood on each corner around the building, smiling and wishing "buenos dias" to passers-by instead of casting stony glares. Curious Cubans clustered around the forest of flagpoles at the front of the embassy, snapping photos as U.S. tourists posed for selfies in front of the building.

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. The U.S. was represented by Assistant Secretary of State for Western Hemisphere Affairs Roberta Jacobson, who led U.S. negotiators in six months of talks leading to the July 1 announcement, and Jeffrey DeLaurentis, the chief of the U.S. Interests Section in Havana who will now become charge d'affaires.

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.

Rodriguez met in Washington with Secretary of State John Kerry, who will travel to Havana Aug. 14 to preside over a flag-raising ceremony there. Rodriguez was the first Cuban foreign minister to set foot in the State Department since 1958.

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. And, Conrad Tribble, the deputy chief of mission for the United States in Havana, tweeted: "Just made first phone call to State Dept. Ops Center from United States Embassy Havana ever. It didn't exist in Jan 1961."

Though normalization has taken center stage in the U.S.-Cuba relationship, 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 Obama's moves on Cuba.

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 Sen. Patrick Leahy, D-VT, a supporter. However, New Jersey Sen. 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."

Obama has sought engagement with communist 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.

Declaring the hostile, longstanding policy a failure, Obama said work would begin apace on normalization. The U.S. removed Cuba from its list of state sponsors of terrorism in late May. On July 1, issues of American diplomats' access to ordinary Cubans were resolved and the July 20 date was set for the restoration of full relations.