Havana, Cuba (CNN) -- The cake has been cut. The guests have all gone home. And now, even the honeymoon may be over.
What began as a hopeful "new beginning" for U.S.-Cuba relations, as President Obama once put it, may be settling back into the same old relationship that has gripped the two Cold War foes for half a century.
In his first column of the new year, former Cuban leader Fidel Castro took his most recent swipe at the U.S. president in an article published in state media this week.
Castro criticized Obama on issues ranging from U.S. troop escalation in Afghanistan to his participation in a climate summit in Copenhagen, Denmark.
Obama exited through a back door "like a dwarf," Castro wrote Monday in the nation's state-run daily newspaper, referring to Obama's behind-the-scenes dealings at the summit.
The aging Communist leader has become a sort of columnist-in-chief, routinely commenting on world affairs and rendering opinions about U.S. foreign policy. He ceded the presidency to his younger brother, Raul Castro, in 2006, but routinely emerges on the world stage through his columns.
The elder Castro's "reflections," as he calls them, are known for their hard-line stances against U.S. administrations.
Obama has been a recurring subject, appearing in roughly one quarter of Castro's columns last year.
Up until December, Castro's words were commonly couched in dialogue more friendly than what he dished out to the previous administration of George W. Bush.
"[Castro] started out liking Obama and thinking he would be the un-Bush," said Susan Kaufman Purcell, director of the Center for Hemispheric Policy at the University of Miami. "But he is generally harder on Republicans," she added.
"With the Democrats, he may allow himself to harbor some hope that things will change ... but ultimately gives up on them too," she said.
On the streets of Havana, there still appeared some hope.
"We are all happy to see they've elected a black president," said one Havana resident who did not provide his name. "We have high hopes he does a good job."
Castro seemed to share that sentiment at first, even once referring to the American president's apparent "youth and vigor," and initially defending the decision to award him the Nobel Peace Prize.
But his recent tenor may signal a move back to politics as usual.
In a letter to Venezuelan President Hugo Chavez, Castro condemned what he described as aggressive moves by Washington throughout the region.
"The intentions of the empire are obvious," Chavez read aloud at the Bolivarian Alternative for the Americas summit in Havana. "This time behind the friendly smile and African-American face of President Barack Obama."
Tensions flared in Venezuela last year when the Obama administration reached a deal with the president of neighboring Colombia, Alvaro Uribe, that granted U.S. military personnel greater access to Colombian bases.
The mood further soured when Cuban President Raul Castro led the country's largest military exercise in nearly five years, calling on Cuban forces to be ready for an American invasion.
"The political, military situation, which characterizes the confrontation between our country and the empire, can go from a relatively normal situation to a much more urgent, confrontational, aggressive one in a month, a week, or even in a night," Gen. Leonardo Andollo Valdez said on Cuban state television.
Adding to the downward spiral in relations, an American contractor was detained in Cuba last month for distributing communications equipment under a program subcontracted by the U.S. State Department.
The contractor was working for a group called Development Alternatives, Inc., a Maryland-based development firm, which later issued a statement saying it had won the contract to help implement a U.S.-administered "Cuba Democracy and Contingency Planning Program."
The program is designed to support rule of law and human rights, political competition and consensus-building in Cuba, the group said in its statement.
Despite Cuban government assertions that such programs are meant to destabilize the country, the U.S. State Department denies claims of clandestine intent.
"These are not secret programs and we regularly brief Congress and staff about these programs all the time," U.S. State Department spokeswoman Virginia Staab told CNN.
Cuba begged to differ.
"The enemy [United States] is as active as always," Raul Castro said during a National Assembly speech, referring to the detained contractor.
There have been a few signs of improved relations between the Cold War adversaries, which many Cubans hope will eventually put an end to the near half-century U.S. trade embargo.
In April, President Obama lifted all restrictions on the ability of Cuban Americans to visit relatives in the U.S., as well as on remittances to the island nation.
Since then, however, the diplomatic warming may have stopped.
"You make some liberalizing moves and wait for a response, and it always ends the same," Purcell told CNN. "You end up saying, 'Well, the ball is in their court now'."
In the latest example of heightened tensions, Cuba summoned the top U.S. diplomat in Havana, Jonathan Farrar, to protest heightened screening measures for Cubans flying into the United States, according to Josefina Vidal, head of the North American department at Cuba's Foreign Ministry.
She said Farrar had been presented with a formal protest.