The United States expressed public concern Monday about the close ties between the governments of Cuba and Venezuela, amid suggestions by U.S. officials they may be working together to fan anti-American sentiment and undermine democratic governments in Latin America.

The comments by the State Department were a rare public expression of what has been growing private concern within the Bush administration about the relationship between the Fidel Castro's communist government in Cuba and the administration of Venezuela's maverick President Hugo Chavez.

The briefing remarks by State Department spokesman Adam Ereli stopped short of accusing Venezuela of anti-democratic activities. But Mr. Ereli said Cuba's efforts in that area over the years have been clear, and that the United States is concerned about the close relationship that has developed between the Castro government and Mr. Chavez. "We are concerned about any action that might impede free and fair democratic processes throughout the hemisphere. I would note that the Castro regime, as is well-known, has a long history of attempting to undermine democratic governments throughout the region. And for that reason, the close ties between the government of Venezuela and the government of Cuba raise concerns among Venezuela's democratic neighbors," he said.

The Associated Press reported Monday that U.S. officials believe that oil-rich Venezuela has been supporting Cuban political activity in the region, and that Venezuelan money may have been decisive in the ouster of Bolivia's elected pro-American president, Gonzalo Sanchez de Lozada last October.

It also said U.S. officials believe that despite denials, Mr. Chavez has supported left-wing Colombian FARC and ELN guerrillas, and allowed them to use Venezuelan territory as a springboard for attacks inside Colombia.

On the latter issue, Mr. Ereli said the United States has expressed concern with Venezuelan authorities about what he said were reports of "terrorist elements operating along Venezuela's border with Colombia," and continues to monitor the situation.

In a related development Monday, the State Department applauded the joint Ecuadoran-Colombian security operation that produced the capture in Quito last Friday of a senior FARC guerrilla commander, Ricardo Palmera, also known as Simon Trinidad.

Mr. Ereli congratulated the Ecuadoran police who made the arrest for their high level of professionalism, and described the apprehension Mr. Palmera, the guerrilla group's chief ideologue, as "a blow to terrorism throughout the region."

The spokesman said while the United States has long been providing training and equipment to the Ecuadoran police, it was not involved in the arrest.