Pentagon officials have inspected several military bases in the United States that could potentially replace the detention center at Guantánamo Bay, Cuba, if President-elect Barack Obama fulfills his pledge to close the camp there. The sites visited included Fort Leavenworth, Kan., and Camp Pendleton, Calif., military sources said.

The visits were part of a formal review of military bases and prisons initiated several weeks ago in response to public statements by Mr. Obama. The study, which military officials described as preliminary, has already drawn criticism from Republican legislators who oppose the closing of the Guantánamo Bay center and fear that the relocation of terrorism suspects to their districts could attract terrorist violence.

“The department is examining any number of options and what it would take to implement such a decision if it were made,” said Cynthia Smith, a spokeswoman for Defense Secretary Robert M. Gates. Mr. Gates has also said the Guantánamo center should be closed.

A Pentagon official with knowledge of the review, speaking on the condition of anonymity because he was not authorized to discuss the matter, said the military was also considering federal prisons but would not say whether any Bureau of Prisons facilities had been physically inspected. The Justice Department was not involved in any such review of prisons, a spokesman, Dean Boyd, said, but he noted that agency officials were having discussions with the Obama transition team about national security matters, including the future of the Guantánamo center.