ROME — On the second anniversary of the start of his papacy, Pope Francis announced that the Roman Catholic Church would mark an extraordinary Holy Year in December, though he might not be celebrating many more anniversaries in the future.

“I have the feeling that my pontificate will be brief — four or five years; I do not know, even two or three,” he predicted in an interview with a Mexican broadcaster. “Two have already passed. It is a somewhat vague sensation,” the pope said, reiterating his belief that “the Lord has placed me here for a short time, and nothing more.”

Leaving open the possibility that he might follow in the footsteps of his predecessor, Benedict XVI, who became the first pope to step down in 600 years when he did so in 2013, the pope said Benedict “should not be considered an exception, but an institution.”

“Maybe he will be the only one for a long time, maybe he will not be the only one,” said the pope, 78, adding that Benedict opened an “institutional door.”