The D.C. police department is ramping up security for inauguration week, when as many as four million people are expected to celebrate the swearing-in of Barack Obama as the nation's 44th president.

The celebration could get rowdy after the city council passed "emergency" legislation allowing bars to stay open 24 hours and to serve alcohol until 5 a.m. from Jan. 17 to Jan. 21.

Nearly 100 law enforcement agencies will deploy an additional 4,000 officers to help D.C. police in the days leading up to the inauguration.

But some police officials fear that won't be enough.

Kristopher Baumann, head of the D.C. police union, envisions trouble surfacing in neighborhoods away from the festivities with an overtaxed police force unable to respond.

"Here's the bottom line: Our responsibility is protect citizens," said Baumann, chairman of the Fraternal Order of Police Lodge 1, which represents D.C. officers.

"D.C. is still a violent city and we need resources to respond if citizens need us," he said. The inauguration extension is "putting us in a position where we won't be able to do that."

But police department officials suggested they were prepared to meet the challenges.

"Violent crime actually is down in the district," police spokeswoman Traci Hughes told FOXNews.com, "and we don't have any reason to believe that the activities during the inauguration week, including the extended hours of the bars and clubs, will increase violent activities."

D.C. Police Chief Cathy Lanier told a local radio station that she wanted some bars and nightclubs to be excluded from the late-drinking legislation, but her concerns were ignored, giving her department more work during what will likely by a historically busy period.

"Drinking and driving, drinking to excess always add to our public safety challenges," she said. "And with the inaugural events and the extended hours in the bars, we have additional challenges now we have to deal with."

But Hughes said they will be ready.

"We prepare for every contingency," she said. "The event is going to be historic. We've never seen anything like it but it doesn't mean we're not prepared."

Bar owners pushed for the extended hours to rake in the tourist dollars, and the D.C. council went along with it because the district gets a piece of the action.

"I'm not getting into the moral issue of drinking. That's for preachers to do," D.C. Councilman Marion Barry told FOX News. "But from a tax point of view, the more places that are open, the more taxes we get."

D.C. Councilman David Catania told FOX News that the inauguration will not attract the rowdy crowds that one might expect.

"What we're trying to do is open the city up for a very brief four-night period, and understand that we're all adults celebrating important change in the government of our country," he said.

For his part, Baumann said he hopes his gloom-and-doom scenario doesn't occur.

"I hope this is one of those times where I'm dead wrong," he said.

FOX News' Brian Wilson contributed to this report.