Secretary of State George Shultz vowed that a bomb attack on his motorcade will not intimidate the United States or Bolivia in their fight against drug traffickers.

"We will not be intimidated and the Bolivian government will not be intimidated," Shultz said at a press conference after the attack on Monday.No one was injured, but four motorcade cars were damaged when the remote-controlled dynamite bomb blew up near the road moments after Shultz passed.

Shultz continued his scheduled meetings with Bolivia's top leaders on cooperation against drug trafficking and other issues.

Some Bolivian officials think the explosives, which were evidently too weak to kill Shultz, were set off by drug traffickers in an effort to intimidate the secretary of state and Bolivian officials.

In an anonymous call to a local radio station, a person said the attack had been carried out by a group calling itself the "Simon Bolivar Command."

The radio gave no further details, and there was no immediate information about the group whose name derives from a 19th century hero of Latin America's independence wars against Spain.

Shultz did not accuse a specific group but said in a speech to Bolivian dignitaries:

"The traffickers want us to look the other way. The terrorists want us to run and hide. You have picked the wrong people.

"The enemies of decency and democracy will not get their way."