"The U.S. Embassy denied the minister an entry visa," an official from the ministerial staff said by phone from Sukhumi, the capital of the unrecognized South Caucasus republic.
The source said Shamba wanted to attend a UN Security Council session in New York that will discuss a resolution on Georgia.
Russia recently raised the issue of Georgia's "provocative actions" in its breakaway territories with the Security Council but its initial draft resolution was rejected by the U.S. and Great Britain, prompting Russia to submit a second, milder version.
Tensions between Russia and Georgia have escalated since a spying row in late September, when Georgia arrested several Russian officers on espionage charges.
The official did not rule out that "lack of time" was to blame for the visa denial. "The visa application was submitted only two days prior to the scheduled departure for the U.S.," he said.
The embassy said it will not comment on private visa-related cases, as American law prohibits it.
