US Defence Secretary Donald Rumsfeld has expressed concern about plans by Venezuela to buy 100,000 Russian AK-47 assault rifles.
Rumsfeld was visiting Brazil when he made the remarks
Speaking during a visit to Brazil, Mr Rumsfeld said he could not see what Venezuela would do with the weapons.
He added he personally hoped the purchase would not go ahead.
Relations between the two countries have been tense since Venezuelan President Hugo Chavez accused the US of trying to kill him.
Washington has suggested the rifles could end up in the hands of the Colombian rebel group Farc - a claim rejected by Venezuela.
A senior US defence official told the Associated Press news agency the weapons were expected to arrive in a few months' time.