Venezuelan President Hugo Chavez called Friday for a cooling of tensions with Colombia and predicted a summit of Latin American presidents in this seaside capital "is going to be positive."

Still, the leftist presidents of Venezuela and Ecuador kept the pressure on Colombia as they arrived late Thursday. The Rio Group summit, due to begin later Friday morning, was to have focused on energy and other issues but the diplomatic crisis in the Andes now has center stage.

It was triggered by a deadly Colombian cross-border raid into Ecuador on Saturday that killed a senior Colombian rebel.

"People should go cool off a bit, chill out their nerves," Chavez told journalists at his hotel before leaving for the summit, being held in the foreign ministry of the Dominican Republic. "I think the meeting today is going to be positive, because it is going to help the debate. We have to debate, talk, and this is the first step toward finding the road."

Chavez has ordered thousands of troops and tanks to Venezuela's border with Colombia and threatened to slash trade and nationalize Colombian-owned businesses. Ecuadorean President Rafael Correa has also sent troops to the border.

The summit marks the first face-to-face encounters between Chavez, Correa and Colombian President Alvaro Uribe since the international crisis began.

Correa told reporters he wants Uribe to apologize for the attack in Ecuadorean territory, as well as his "formal and firm commitment" that Colombia will never "violate" the sovereignty of another country.

On his arrival in Santo Domingo late Thursday, Chavez took shots at Colombia and the United States, which has supported the Andean nation with more than $4 billion in counterinsurgency and anti-drug aid since 2000.

"The U.S. empire has taken over Colombia," Chavez said.

Chavez claimed the strike that killed Raul Reyes, a top leader of the Revolutionary Armed Forces of Colombia, or FARC, was "planned and directed by the United States." Later, he said he had information that "gringo soldiers" participated in the attack, but provided no evidence to back the claim.

Earlier this week a spokesman for the U.S. Southern Command, Jose Ruiz, would neither confirm or deny the U.S. military took part in the attack that killed Reyes and 23 others.

Uribe, who is hugely popular among Colombians for efforts to crack down on the FARC, which finances itself through kidnapping and drug trafficking, declined to comment on the crisis as he arrived for a meeting with Dominican President Leonel Fernandez.

Earlier, Uribe defended the attack as necessary given Ecuador's inaction against Colombian rebel camps in its territory. Colombia complains that rebels take refuge across the border in neighboring countries and has accused their leftist leaders of backing the rebels -- a claim the leaders deny. Uribe has said he won't send Colombia troops to the border.

Friday's opening of the presidential summit will mark the first face-to-face encounters between Uribe, Chavez and Correa since the international crisis began.

The crisis widened Thursday when Nicaragua broke off relations with Colombia over the attack inside Ecuador. Nicaraguan President Daniel Ortega, who was also attending the summit, is an ally of Chavez and Correa.

Before the presidents began arriving here Thursday night, foreign ministers from a host of countries drafted a statement saying national sovereignty must be respected. The draft, to be submitted to the Latin American presidents on Friday, mirrors one this week from the Organization of American States, said Chilean Foreign Minister Alejandro Foxley.

But Salvadoran President Tony Saca said as he arrived for the summit Thursday that the Colombian government should be able to defend its citizens.

"We need to understand Colombia has the legitimate right to go after terrorists .... wherever they may be, of course without harming the sovereignty of another country," Saca told reporters.

Mexican President Felipe Calderon said he hopes that "we can have a dialogue in a sensible way to find a peaceful solution" at the summit. Calderon added that he doubted one would be found quickly.

Uribe has refused to rule out future military incursions into Ecuador or Venezuela, saying he first needs assurances from Correa and Chavez that they are not harboring rebels.

In Ecuador, Security Minister Gustavo Larrea said the army captured five suspected FARC rebels on Thursday. The suspects were nabbed "a few meters from the Colombian border," in the general area where the raid took place, Larrea told a news conference.