The Obama Administration could use lethal force on Americans within the United States and without trial during "an extraordinary circumstance," Attorney General Eric Holder said on Tuesday.

In a letter to Sen. Rand Paul (R-KY), Holder said the Administration favored the use of law enforcement over the military when it came to fighting terrorist threats within the country. However, Holder refused to rule out the possibility that the President of the United States could use a drone strike on U.S. soil in an extreme situation.

"As members of this administration have previously indicated, the US government has not carried out drone strikes in the United States and has no intention of doing so," he wrote. "As a policy matter moreover, we reject the use of military force where well-established law enforcement authorities in this country provide the best means for incapacitating a terrorist threat."

"The question you have posed is therefore entirely hypothetical, unlikely to occur, and one we hope no president will ever have to confront," Holder added.

"It is possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the President to authorize the military to use lethal force within the territory of the United States. For example, the president could conceivably have no choice but to authorize the military to use such force if necessary to protect the homeland in the circumstances like a catastrophic attack like the ones suffered on December 7, 1941, and September 11, 2001," Holder continued, referring to the attacks on Pearl Harbor and the World Trade Center, respectively.

Paul had threatened to hold up the nomination of John Brennan as CIA director over questions about whether the Administration believed it could use drone strikes within the United States. In a separate letter, Brennan told Paul that the CIA had no authority to conduct lethal operations within the country.

"The U.S. Attorney General's refusal to rule out the possibility of drone strikes on American citizens and on American soil is more than frightening - it is an affront the Constitutional due process rights of all Americans," Paul said in a statement.