The U.S. attorney's office said the charges were against Chao Tung "John" Wu, 51, and Yi Qing Chen, 41, both naturalized U.S. citizens born in China and now living in California.
The two men were approached by an undercover agent who told them that the missiles would later be sent outside the United States. The bribes, including one for $2 million, were to be paid to foreign officials. Countries involved were not identified.
Wu's attorney, Gerson Horn, said an undercover agent had tried to buy weapons from Wu and that Chen was allegedly involved in the negotiations. He said the agent "initiated the negotiations and persisted in the negotiations but it never bore fruit ... with either one of them."
He said his client is innocent and that the case was "conceived, nurtured and orchestrated by the undercover agent, who worked this case for a number of years."
Horn also said no weapons or weapons components changed hands.
An attorney for Chen did not immediately return a call for comment.
The charges marked the first time an anti-terrorism statute, adopted in 2004, has been used. It calls for a mandatory minimum sentence of 25 years and the possibility of life in prison without parole if convicted.
The men have been in custody since August when they were arrested as part of Operation Smoking Dragon, a U.S. undercover investigation into smuggling operations in Southern California. The men were originally charged with conspiracy to distribute methamphetamine and Ecstasy and importing millions of counterfeit cigarettes.
"Today's indictment shows a willingness of the smugglers to acquire practically anything for importation, no matter how dangerous or destructive," U.S. Attorney Debra Wong Yang said in a statement.
An arraignment hearing on the new charges is scheduled for Monday.