LATIN America may have stood back from the brink of war this weekend as Colombia apologised for a bloody incursion into Ecuador in pursuit of Farc guerrillas, but the crisis heralded the return of US involvement in the region, exposing the deep rift that lies between Colombia, Washington's staunchest regional supporter, and many of its neighbours.

At a meeting of the Rio Group of Latin American countries in the Dominican Republic, a vicious verbal spat between Colombian president Alvaro Uribe on the one hand, and Venezuelan president Hugo Chavez and Ecuador's Rafael Correa on the other, gave way to a charade of handshakes and laughter - and a reminder from Argentina's president Cristina Fernandez de Kirchner that in view of the "hysteria" she had witnessed at the summit, it was clear that women were "more rational than men".

"This is a summit from God," said an exuberant Chavez, after the presidents agreed to condemn the interference of one country in the affairs of another, without specifically mentioning Colombia. Uribe in turn agreed to respect the sovereignty of other nations, withdrew a threat to take Chavez to the International Court of Justice in the Hague, and agreed to withdraw Colombian warships from disputed waters off Nicaragua. Nicaragua, which had broken off ties with Colombia along with Venezuela and Ecuador, promptly restored links with Bogota.

Although the US - not a member of the Rio Group - was not represented at the summit, Washington was on everyone's mind. Earlier, Chavez had heaped abuse on Uribe, describing him as a lackey of the United States. He said that the US had orchestrated the helicopter gunship operation which left the Farc's second-in-command, Raul Reyes, and around 20 other rebels dead. Another rebel leader, Ivan Rios, was reportedly killed by a Farc deserter, while the reported deaths of four Mexicans among the guerrillas gave a wider regional dimension to the crisis. Would Colombia now attack Mexico, accusing it of meddling in its internal affairs?

Bogged down by five years of war in Iraq, the Bush administration appeared to have taken its eye off the ball as most of Latin America tilted left. Colombia, the third-biggest recipient of US military aid in the world after Israel and Egypt under Plan Colombia (ostensibly a war against drugs) is Washington's only real foothold in the region. Chavez, who along with Ecuador's Correa rushed troops to the Colombian border, described the incursion as the first manifestation in Latin America of "the Bush doctrine" of pre-emptive strikes, "as witnessed in Iraq and Afghanistan".

But Uribe claimed his country had endured more than 40 attacks by Farc from Ecuador since 2004; that a laptop recovered from the debris of the Farc camp contained evidence that both Chavez and Correa were linked to Farc; and that Correa's presidential election campaign had even been financed by the rebels, who have fought a 43-year war against the Colombian state.

"How can one believe one who has lied and lied again?" retorted Correa. "Ecuador could argue, just as you accuse us of letting the guerrillas in, that you let the guerrillas out." He said he had been in touch with Farc as part of an attempt to secure the release of hostages, including Ingrid Betancourt, a French Colombian and former presidential candidate. The hostages are due to be freed on Friday, Correa said, claiming that Uribe had been aware of this. "How low can one stoop?" he said of Uribe.

The contents of the laptop found in the rubble of the Farc camp led to another surprise development: the arrest of former KGB agent Viktor Bout, an international arms dealer, in Bangkok. Bout is wanted in the US to stand trial on a charge of conspiracy for attempting to smuggle missiles and rocket launchers to the Farc. Colombian officials said the laptop also held information that suggested the Farc guerrillas were seeking to purchase uranium for the production of a "dirty bomb".

The timing of the laptop revelations and the arrest of and linking of Bout to Farc suggests the US has again turned its focus on what it once referred to as its own "backyard".

A report by three US think-tanks this weekend warned of a "disturbing transformation" of US foreign policy decision-making from the State Department to the Defence Department.

The report, by the Washington Office on Latin America, the Centre for International Policy and the Latin American Working Group Education Fund, said this trend was likely to "diminish congressional, public and even diplomatic control over a substantial lever and symbol of foreign policy. It will undercut human rights values in our relations with the rest of the world, and increase the trend toward a projection of US global power based primarily on military might."