An unprecedented security operation is under way in Washington ahead of Barack Obama's inauguration as US president. With estimates of up to a record two million people attending on 20 January, the event has been designated a "national special security event". Reports suggest more than 20,000 police officers, troops and security agents are involved. The Obamas are due to check into Blair House, the presidential guest house opposite the White House. The security operation for Mr Obama's inauguration will see surface-to-air weapons on standby, fighter jets providing air patrols and gunboats patrolling the Potomac River. "We understand the historical significance of his election, and we pay attention to that. We look at every single aspect of protection... any factor that you could imagine," Secret Service spokesman Ed Donovan told French news agency AFP. Homeless As part of the operation, hundreds of homeless people are being encouraged to move out of the security zone to shelters in the city's outer neighbourhoods. "Everyone has to be out of the perimeter by (Monday)," DC Council member Tommy Wells told the Washington Post. Meanwhile, Mr Obama posted a four-minute video message on the internet. He warned those coming to the capital to expect "long lines, a tough time getting around and, most of all, a lot of walking on what could be a very cold winter day". The Obama family, which spent 10 days staying in a hotel, is also due to take a step closer to the White House. They are checking into Blair House, the historic guest house, across Pennsylvania Avenue from their future residence. The next First Lady also appears to be thinking about the internal decorations of the White House. Michelle Obama has chosen Los Angeles-based designer Michael Smith to decorate the private quarters of the executive mansion, transition officials told AP news agency. Mr Smith has designed the homes of Hollywood stars Dustin Hoffman, Michelle Pfeiffer and Steven Spielberg, as well as model Cindy Crawford and media mogul Rupert Murdoch. Source: BBC