It was a moment that promised to define a new era in U.S.-Latin American relations: Obama greeted Hugo Chávez at the Summit of the Americas with a smile and a handshake, and Chávez responded with a gift and a heavily accented “I wanna be your friend.” The Cold War-style chasm between Washington and the leftist leaders of the Andes that had widened during the Bush administration finally seemed to be narrowing a bit.

But a nearly completed agreement between Colombian President Alvaro Uribe and the Obama administration to grant the U.S. military access to Colombian bases is rapidly undermining whatever diplomatic progress was made in that fleeting moment.

The Uribe administration announced on July 12 that it had nearly reached an agreement on the terms of a decade-long lease to allow U.S. military personnel to use Colombian military bases to conduct anti-drug trafficking and anti-terrorism operations. No draft of the agreement has yet been made public. The increased access would serve to replace the U.S. lease at Manta, Ecuador, the only U.S. base of operations in South America until the lease was allowed by the Correa administration to expire this month.

President Uribe defended the agreement as a necessary step in his administration’s fight against drug traffickers and Marxist guerrillas at a public event in Santa Marta last week. “This agreement guarantees continuity in the era of an improved Plan Colombia,” he said, referring to the pact that has funneled $6 billion in U.S. aid to the Colombian government and military.

The lease agreement has drawn criticism from Colombian congressmen across the political spectrum, who argue that the executive does not have the authority to allow foreign troops into the country. Liberal Senator Juan Manuel Galán claimed that the Uribe administration “bypassed the Senate.” Senator Jairo Clopatofsky, an uribista of the right-wing Partido de la U, echoed Galán’s criticisms.

Senator Jorge Robledo of the left-wing Polo Democrático Alternativo Article 173 which states that the decision to “Permit the transit of foreign troops through the territory of the Republic” falls to the Senate.

Colombian and U.S. authorities have sought to calm critics by reassuring them that the agreement will not constitute the creation of an autonomous zone of U.S. military operation. “Any activity performed within the framework of the agreement has to be coordinated and authorized by the Colombian authorities,” said Minister of Defense General Freddy Padilla de León. U.S. Ambassador to Colombia William Brownfield has reiterated the same point and has emphasized that the increased U.S. presence should not be misconstrued as a foreign military base. “They have their bases. This is a question of access,” he said.

The national controversy provoked by the possibility of an increased U.S. military presence in Colombia pales in comparison to the international dispute it has caused. As a neoliberal island in a Bolivarian sea, Colombia’s decision to host more U.S. military personnel has been interpreted by neighboring Ecuador and Venezuela as a security threat. Consequently, Colombia’s diplomatic and commercial relations with its neighbors are crumbling faster than a UNESCO World Heritage Site.

Colombia’s relations with Ecuador have remained tense since March 2008, when the Colombian military attacked an encampment of the Fuerzas Armadas Revolucionarias de Colombia (FARC) located along the border, killing rebel leader Raúl Reyes and 16 other guerrillas. The Correa administration recalled its ambassador to Colombia in protest against the violation of Ecuador’s sovereignty.

The latent conflict erupted once more in June, when Ecuador filed an arrest warrant with Interpol against former Defense Minister Juan Manuel Santos for the murder of an Ecuadoran citizen killed during the March 2008 offensive. Santos is a close ally of president Uribe and rumored to be a presidential contender in 2010 if Uribe does not seek re-election. The Uribe administration responded by releasing a video of FARC commander Jorge Briceño claiming that the FARC contributed $100,000 to Corrrea’s presidential campaign. The video, which the Colombian government says was recovered from the computer of alleged FARC member Adela Pérez last May, was submitted to Interpol and leaked to the media. Correa denies any support of illegal armed groups in Colombia and has demanded that the FARC “say if they have donated money and to whom.” The Economist reports that Ecuador’s electoral commission has certified his campaign contributions.

Colombia’s relations with Ecuador were further soured by Uribe’s invitation of more U.S. troops, since Correa had only recently expelled U.S. military personnel from the Ecuadoran base at Manta. Correa promised in his presidential campaign to shut down the only U.S. military base in South America, although he later offered to renew it if the U.S. agreed to let Ecuador establish a military base in Miami. “If there's no problem having foreign soldiers on a country's soil, surely they'll let us have an Ecuadoran base in the United States,” he said.

Correa has announced that any further aggressions from Colombia will invite a military response. An increased U.S. military presence in Colombia promises to ratchet up tensions with Ecuador. The U.S. president, in his first major statement on Latin America policy, said that “In an Obama administration, we will support Colombia’s right to strike terrorists who seek safe-haven across its borders…”

Venezuela’s Chávez has also characterized the increased U.S. military presence as a threat to his country’s national security. Chávez maintains that the United States supported an abortive coup in Venezuela in April of 2002—a charge that U.S. officials deny, though the Bush administration did not join the 19 Latin American countries who condemned the illegal seizure of power.

Largely in response to the Colombian government’s decision to increase the U.S. military presence there, an indignant Chávez ordered the withdrawal of the Venezuelan ambassador to Colombia on July 27 and has threatened to freeze imports from Colombia and nationalize Colombian companies if he perceives “one more act of aggression.” Venezuela is Colombia’s second largest trading partner, followed by the United States.

The crisis in Colombia-Venezuela relations was stoked by allegations from the Uribe administration that the Venezuelan government supplied Swedish anti-aircraft rocket launchers to the FARC. The Colombian military seized the weapons in question at La Macarena in October of 2008, but did not notify the Venezuelan government until early this month, according to a press release. The Swedish government has requested an explanation from the Chávez government. Chávez denied the allegations, saying “Anyone can take a rifle [sic] and put a Venezuelan seal and a serial number on it.”

Colombia’s more distant neighbors have also taken a keen interest in the military agreement. Brazilian President Lula da Silva commented that “An American base in Colombia doesn’t please me.” Chilean President Michelle Bachelet, who was tortured along with her father by the Pinochet government following a military coup supported clandestinely by Washington, has called a meeting of the Union of South American Nations on August 10 in Quito, Ecuador, to discuss the issue. President Uribe is not expected to attend.

Far from the smiles and handshakes of April, the Obama administration now finds itself at the center of Latin America’s most explosive inter-state crisis. The “New Partnership in the Americas” promised by Obama on the campaign trail and at the Summit of the Americas looks increasingly elusive.