Barack Obama [Images], who takes office as America's first black President on Tuesday, is the biggest-ever assassination target in US history, a media report said.

47-year-old Obama has taken on the most important job. But it is also the most dangerous, and he knows that there are extremists who want him dead, the Daily Star reported.

White supremacists have vowed to kill him and the Central Investigative Agency bosses are taking no chances by throwing a ring of steel around his inauguration. In fact, they have turned Washington DC into an impenetrable fortress for the historic ceremony.

The US capital is being guarded by 45,000 soldiers, police, secret agents and National Guards -- all there to make sure that he does not meet the same fate as assassinated 1960s president John F Kennedy.

Jet fighters will also be on standby for the ceremony. Obama will be shielded behind bullet-proof glass and ride in a bomb-proof limo with the Ku Klux Klan, neo-Nazis and al Qaeda all gunning for him, according to the news report.

In fact, US military leaders have also tried to cater for every possible type of terror strike,  from a sniper to a chemical attack.

Intelligence chiefs have reported a huge increase in threats running up to inauguration day. And they have placed snipers on every rooftop around Washington's Lincoln Memorial and Capitol Hill, where Obama delivers his first speech as US President.

"We have seen a lot of chatter. We have seen a lot of discussions and we have seen some information via Internet," FBI Assistant Director Joe Persichini was quoted as saying.