The federal government said it was delaying opening its offices in the Washington area Monday until 11 a.m. because of expected early-morning icy conditions.

The Office of Personnel Management also recommended that federal employees stay off the roads until 9 a.m.

Employees who commute to work will be granted excused absences for the hours of the delay, OPM said in its announcement Sunday evening. (Emergency employees were expected on time, OPM said.)

Alexandria and Prince William County public schools said they would open two hours late.

The DC public schools and the DC government said they would open on time. The DC Superior Court was expected to open on time, a court spokeswoman said.

The U.S. District Court for the District of Columbia said it would open at 11 a.m.

Metro said it would operate expanded morning rush-hour service on its bus and rail lines to accommodate those going to work later than usual.

The actions came as the National Weather Service issued a freezing-rain advisory for much of the Washington region until 6 a.m. Monday. It said freezing rain and drizzle could produce accumulations ranging from a trace to about one-tenth of an inch, which could cause travel difficulties.

In the advisory, issued shortly after 6 p.m., the Weather Service also said sidewalks and untreated surfaces would turn slippery.

Although snow is widely regarded as Washington’s major winter traffic hazard, ice and freezing rain may impede mobility even more severely.

On Jan. 26, 2011, a combination of ice, snow and early dismissals clogged slippery roads, creating what has been described as one of the most severe traffic snarls in the region’s history. That led to a rethinking of the government’s snow plans.

“Freezing rain is the absolute worst,” read a comment posted Sunday on The Washington Post’s Capital Weather Gang site. “Every nightmare commute I’ve endured has involved freezing rain/black ice. I’m working from home.”

The Weather Service advised motorists to “slow down and use caution.”