President Barack Obama visited Federal Emergency Management Agency headquarters on Saturday to get an update on preparations for Hurricane Irene as it charged north along the U.S. East Coast.

Obama, who cut short his vacation on Martha's Vineyard, Massachusetts, by a day because of the hurricane, said it would be a tough slog getting through the storm but praised the federal effort so far.

The hurricane was expected to hit Washington in the early hours of Sunday before hurtling toward New York City. Rainfall expected to total 4 to 8 inches prompted a flash-flood warning for the U.S. capital.

District residents were being urged to avoid driving and use extreme caution because of pooled water and winds expected up to 65 miles per hour Saturday night.

U.S. officials, mindful of the widely criticized slow response to Hurricane Katrina in 2005, have been out in full force urging residents in the path of the hurricane to prepare and take heed of local warnings.

Obama stopped by a FEMA coordination center where federal officials were monitoring the hurricane on large screens and said: You guys are doing a great job.

Pentagon spokesman George Little tweeted that Defense Secretary Leon Panetta had approved a prepare-to-deploy order for 6,500 active-duty military to support hurricane relief efforts if required.

In downtown Washington, by late afternoon skies had darkened, winds picked up and rainwater began to pool on city streets.

In the Maryland capital of Annapolis, Mayor Josh Cohen said public transportation would shut down at 9 p.m. and urged residents of the city on the Chesapeake Bay to stay off the roads.

FLIGHTS CANCELED

Airlines have canceled virtually all flights at Washington-area airports beginning Saturday night.

The Washington National Cathedral, which sustained damage earlier this week during an earthquake that rattled the capital, will be closed the next two Sundays.

The engineers continue to tell us that the building is structurally sound, it's just a matter of the damage that was incurred in the central tower and pieces up there remain precarious, so any of the winds from the storm could cause some of the elements to fall, said Richard Weinberg, spokesman for the cathedral.

Local authorities handed out sandbags to residents living near the rivers that run by the city and television coverage showed lines of cars snaking around RFK Stadium to pick up sandbags.

It's going to be a long 72 hours and obviously a lot of families are going to be affected, Obama said at FEMA, where he sat at a conference table with top federal officials and spoke with state officials in a video conference.

Obama said the biggest concerns were flooding and power outages.

Obama has asked to be updated as necessary throughout the day and overnight, the White House said.