"We have worked diligently to come as close to the goal as possible, but with the large number of documents involved and the holiday schedule we have not met the goal this month," the State Department said in a statement. "To narrow that gap, the State Department will make another production of former Secretary Clinton's email sometime next week."
In March, Clinton came under scrutiny for using her personal email account for official purposes while serving as US secretary of state from 2009 to 2013.
In August, the US intelligence community inspector general reported that at least two of the Clinton emails reviewed by his office contained material classified as Top Secret, which cannot be sent to non-secure accounts. The Clinton presidential campaign disagreed with the initial review findings.
A US District Court judge ordered the State Department in May to make public all of some 55,000 pages of emails that were retained on Clinton's server by the middle of January 2016.