For the first time, Washington will send envoys to Argentina for a meeting of a group that America has never joined — and that even some of its Latin members have criticized as a haven for the region’s dictators. 

President Biden’s delegation to the annual gathering of the Community of Latin American and Caribbean States, or Celac, is led by a former senator, Christopher Dodd, who has long championed Latin America’s leftist leaders.

The 33-member organization was founded in 2011 by Venezuela’s strongman, Hugo Chavez, and is widely considered a benefactor of Latin dictatorships, including Cuba, Nicaragua, and Venezuela.

Countries that have already confirmed attendance at the January 24 Celac meeting at Buenos Aires include Mexico, Peru, Brazil, and Costa Rica. Also confirmed are Venezuela’s president, Nicolas Maduro, and Cuba’s, Miguel Diaz-Canel.  

“If Nicolas Maduro comes to Argentina, he must be arrested immediately for having committed crimes against humanity,” the president of Argentina’s opposition party, Patricia Bullrich, tweeted Thursday. “Justice must act to protect the universal validity of human rights.”

Earlier this month, in an attempt to reinforce bonds with Washington, Argentina’s populist-leftist president, Alberto Fernandez, invited Mr. Biden to attend the Celac parley. America’s ambassador to Argentina, Jorge Arguello, said that “the bilateral bond” between the countries is at one of its “best historical moments.”

Based on mutual visits of government officials, Mr. Arguello says the countries are on a “permanent search to achieve ambitious common goals.” On Wednesday, Mr. Arguello confirmed that a delegation organized by Mr. Biden would be present at the Celac meeting. The delegation will be headed by Mr. Biden’s special advisor for the Americas, Mr. Dodd.

In June, the leftist leaders of Latin America, including Mr. Fernandez, boycotted the Summit of the Americas hosted by Mr. Biden. Following Washington’s refusal to invite the non-democratic leaders of Cuba, Nicaragua, and Venezuela, Mexico’s president refused to travel to the Los Angeles summit.

To avert the planned boycott, Mr. Biden dispatched Mr. Dodd in an attempt to convince the Mexicans, Argentinians, and other no-shows to attend the summit. While Mr. Fernandez did end up flying to the Los Angeles meeting, he railed against the absence of the Cuban, Venezuelan, and Nicaraguan leaders. 

As a senator, Mr. Dodd often sided with leftist leaders in the region and questioned America’s exclusion of Cuba. The embargo “has done nothing to improve the lives of ordinary Cubans, and has done nothing to help bring about a democratic Cuba,” Mr. Dodd said in 2002. “We have to take America’s head out of the sand and call the American policy toward Cuba exactly what it is — a failed policy.”

This month, Mr. Fernandez extended an invitation to Communist China’s Xi Jinping to attend the group’s meeting. In 2021, Beijing and Celac signed an agreement to promote mutual political and economic cooperation. Argentina’s foreign affairs ministry confirmed Wednesday that Mr. Xi will send a delegation to the Celac meeting. No further details were announced.

Another surprise is the return of Brazil to the group, which it has shunned in the past. Concerned that the organization benefited the region’s dictatorships, Brazil’s former president, Jair Bolsonaro, decided in 2019 to withdraw Brazil’s from the group.

A mere five days after President Lula da Silva had taken office on January 1, the Brazilian ministry of foreign affairs announced that it had informed Celac membership of “the reincorporation of Brazil” to the group. 

“The return of Brazil to the community of Latin American States is an essential step for the recomposition of our diplomatic heritage and the full reintegration of the country into the international community,” the statement said.

Mr. da Silva is expected to arrive at Buenos Aires on January 23, a day before the summit, to meet Mr. Fernandez. “We are on the same path, looking for the same destiny for our countries and South America,” Mr. Fernandez said. “We are waiting for Lula on an official visit on the 23rd, and we hope to be able to move forward with concrete actions.”

The members who announced their absence are Mexico’s president, who rarely leaves the country, Peru’s president, Dina Boluarte, and Ecuador’s, Guillermo Lasso. Argentinian press outlets report that the relationship between Messrs. Lasso and Fernandez was damaged last month when Argentina gave political refuge to an Ecuadorian politician, Maria de Los Angeles Duarte. She was allegedly involved in a corruption case with a former president, Rafael Correa. 

At the moment, Mr. Fernandez is being widely criticized for his attempt to impeach four justices of Argentina’s supreme court of justice. The move followed the court’s ruling that the federal government must repay 2.9 percent of federal funds to the City of Buenos Aires, which were withdrawn in 2020. The capital’s governor, Horacio Rodriguez Larreta, is a right-wing opponent of Mr. Fernandez. 

In Brazil, Mr. da Silva is leading an investigation into the January 8 attack on Brasilia’s government institutions. In the Brazilian version of Washington’s January 6, 2021, riot, Mr. Bolsonaro’s supporters invaded the Supreme Court, the Congress, and the Planalto Presidential Palace at the capital. The anti-government demonstrators refused to recognize the October 30 presidential elections in which Mr. Bolsonaro was defeated. 

The Celac summit is the second attempt by the region’s newly elected leftist leaders to meet. In December, an event hosted by Mr. Lopez Obrador was canceled after Peru’s president, Pedro Castillo, was deposed by the Lima parliament on allegations of corruption. Ms. Boluarte assumed office shortly after. Since then, countrywide protests have erupted, with throngs of Mr. Castillo’s supporters calling for his reinstatement to power.