"Certainly, I'm concerned. I can't imagine what's going to happen to 100,000 AK-47s. I can't imagine why Venezuela needs 100,000 AK-47s, and I just personally hope that it doesn't happen," he said after meeting with Brazil's vice president and minister of defense, Jose Alencar.

"And I can't imagine if it did happen that it would be good for the hemisphere," Rumsfeld added, noting US concerns that rebels from the leftist Revolutionary Armed Forces of Colombia (FARC), or other illegal armed groups in the region might get hold of some of the weapons.

According to a senior Pentagon official, "it may be a lot more than a 100,000 ... up to 300,000."

The official said Venezuelan President Hugo Chavez's army "only has 32,000 men, the national guard 30,000. Those two forces are already well armed."

"It's a vast oversupply," the official said privately.

"Our first concern is accountability. They could end up easily in the hands of terrorists (and) internally, what he (Chavez) is trying to do is try to create Cuban-style popular militias."

After his talks with Alencar, Rumsfeld met with Brazilian President Luiz Inacio Lula da Silva. He was then scheduled to fly to Manaus, in the Amazon region, later in the day, followed by a stop in Guatemala.