WASHINGTON — The Department of Veterans Affairs said Monday it now has fewer than 100,000 disability claims older than four months, a “historic milestone” that is one-sixth the size of a long-term backlog that reached a record 611,000 claims in 2013.

Allison Hickey, the VA’s undersecretary for benefits, said the current backlog of 98,535 claims older than 125 days is the lowest since the agency started measuring it in 2007.

The decrease has not come at the expense of quality, Hickey said. Accuracy of disability decisions has improved from about 83 percent in 2011 to 91 percent today, she said.

The gains were achieved in part through use of mandatory overtime for employees in the benefits division, a practice Hickey says officials hope to stop in September.

Mandatory overtime has been effect for nearly three years but “is not sustainable,” Hickey said, adding that she is confident that recent gains will not be sacrificed once mandatory overtime concludes.