Gandhi rejected claims this year that his revenue projections have been too low. (Sarah L. Voisin/The Washington Post)

District finance officials estimate that, with three days remaining in its fiscal year, the District government is running a nearly $140 million operating surplus.

Chief Financial Officer Natwar M. Gandhi disclosed the figure in Friday letter to Mayor Vincent C. Gray (D) and D.C. Council Chairman Phil Mendelson (D-At Large).

About one-third of the projected $139.5 million surplus is due to an estate tax “windfall,” Gandhi wrote, with another third due to increased income tax withholding.

Of the remainder, about half can be attributed to increased sales taxes , and the rest to $23 million in “automatic traffic enforcement” revenue — that is, speeding and red-light camera fines.

Despite the stronger-than-expected collections this fiscal year, Gandhi is not upgrading his revenue estimates for the next fiscal year, citing ongoing concerns about the potential effects of federal budget sequestration.

A “double whammy” of severe federal cutbacks and the recession they would likely create, Gandhi wrote, “would almost certainly hurt the District’s economy and finances.”

The good news: If Congress can step away from the so-called “fiscal cliff,” Gandhi wrote, “the revenue picture for the District would improve substantially.”

In a statement, Gray said the pending surplus “is affirmation that we are reaping the benefits of our investments in growing the District’s economy and getting our residents back to work.”

The mayor also called on Congress to “act quickly to prevent what everyone agrees is a completely unacceptable and destructive means of reducing the federal budget.”

Gray and Gandhi, you’ll recall, clashed in the spring over what Gray called “unrealistically low” revenue estimates.

The surplus represents about a 1.3 percent variance from the District’s anticipated $10.8 billion in 2012 spending.

Last fiscal year, audited figures showed that the city ran a $240 million surplus, leading Gray and council members to wonder why they had been forced to consider tax hikes and sometimes drastic spending cuts. The final audited number for the current fiscal year won’t be available until late January or early February.

Gandhi’s letter: