President Barack Obama kept a close eye on Hurricane Irene as it charged north along the East Coast on Saturday by visiting the Federal Emergency Management Agency and receiving an evening briefing from top officials.

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.

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.

Obama was again briefed on the storm's track, its impact and response efforts during an evening conference call with senior officials including Vice President Joe Biden, Homeland Security Secretary Janet Napolitano and Energy Secretary Steven Chu. The White House said Obama asked to be kept apprised of developments throughout the night.

The hurricane's core was expected to approach 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 to reach 65 miles per hour Saturday night.

Local authorities reported trees down, including one that crushed a parked car, and power outages.

Washington Mayor Vincent Gray told ABC News he did not know when the dedication of the new Martin Luther King Jr. memorial, postponed because of the storm, would be rescheduled.

We'll come back to this and it will be a great day when we do hold it, he said.

FLIGHTS CANCELED

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 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. The Bay Bridge that connects to the beach communities of Maryland was closed in the evening because of high winds.

Airlines 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, said Richard Weinberg, spokesman for the cathedral. 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.

Local authorities earlier in the day handed out sandbags to residents living near the rivers that run by the city.

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.