Bush said: "They continue to reject the clear will of the Burmese people."
The US move follows weeks of unsuccessful international efforts to get Myanmar's government to end its crackdown on anti-government protesters.
The UN's envoy, Ibrahim Gambari has urged Myanmar to open a dialogue with Aung San Suu Kyi, the detained opposition leader.

Bush said that "in light of the ongoing atrocities by these men and their associates," he had issued an order naming 12 new "individuals and entities" to be covered by the latest measures.