The Treasury has repeatedly said default was unthinkable and that there was no alternative to raising the debt ceiling. Plosser's remarks marked the most extensive public comments yet on preparations for a default from a U.S. official.
A Treasury spokesperson could not be immediately reached for comment.
One aspect of the Fed's contingency planning is purely operational: the Fed is developing procedures about how the Treasury would notify it on which checks would get cleared and which wouldn't, Plosser said.
The Fed effectively acts as the Treasury's bank -- it clears the government's checks to everyone from social security recipients to government workers.
"We are developing processes and procedures by which the Treasury communicates to us what we are going to do," Plosser said, adding that the task was manageable. "How the Fed is going to go about clearing government checks. Which ones are going to be good? Which ones are not going to be good?"