Latin American nations need to be cautious with Iran and its motives when negotiating development of their nuclear capacities, the US defense chief warned here Sunday.

"I think that countries that are dealing with Iran in this arena need to be very cautious and very careful about how they interact with the Iranians in terms of what the Iranians motives might be and what they're really trying to do," US Defense Secretary Robert Gates told journalists ahead of a pan-American defense meeting.

Host nation Bolivia is among countries interested in developing nuclear abilities with Tehran. The United States and some western powers believe Iran's nuclear program is military; Tehran insists it is civilian in nature.

"I don't really know what the Iranians are up to, to really tell you the truth," Gates said.

"If they are talking about civil nuclear power, then all can be safeguarded under IAEA (and) we would have nothing to object" to, he said.

But "I'm not sure the Iranians have an independent capability to help somebody build a civil nuclear capability. Their own capability has been under contract with the Russians" for 20 years, Gates stressed.