Security officials have already received a high-number of permit requests to hold events on public land during the inauguration.

Senior officials are describing the preparations for the inauguration of Donald Trump as the most challenging in recent history, with a potential flood of protesters expected in Washington DC.

There are concerns that protesters and what may be nearly a million Trump supporters in attendance could clash violently at the event which will be broadcast around the world.

The United States will swear in President Trump on January 20, 2017, in a ceremony and parade that begins on the west lawn of the US Capitol building and travels down Pennsylvania Avenue to the White House.

Michael Chertoff, the former secretary of homeland security under Bush who also oversaw Obama's 2009 inauguration, told The New York Times that each inauguration is risky, "but each is risky in its own way".

"I can't think of an inauguration that presented more security challenges than this one," he said.

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REUTERS US president-elect Donald Trump makes his way through the crowd after addressing a Tea Party rally in September.

The inauguration is one of the most high-profile events in the American political calendar, and considerable work is undertaken to make sure there is a peaceful transition of power.

Generally, the National Park Service (responsible for the public land which surrounds the White House) receives a handful of permit applications from groups seeking to host events alongside the inauguration. This year there have been 23 so-far.

Some tens of thousand of analysts, military personnel and law enforcement officers will be contributing to work of 32 agencies tasked with ensuring the event proceeds without issue.

Security costs are expected to exceed $100 million USD.

Presidents Bush and Obama faced their own threats of terrorism, and in the case of the current president, racist threats.

However the kind of protests officials expect Trump will face pose a considerable threat when compared to that of the crowd of two million who attended Obama's inauguration. There were few protesters among this crowd, and not a single arrest, said Christopher Geldart, the director of homeland security for the District of Columbia to The New York Times.

This inauguration, law enforcement on the ground are preparing to confront the angry, anxious crowds seen on the campaign trail in the lead up to Trump's election. The priority is to avoid violent clashes, while allowing groups of both protesters and supporters to hold their events.

"Everybody knows how contentious the campaign was," Geldart said.

"Honestly, what really keeps me up at night around this is the ability for us to just allow folks to come in, express their views and leave safely."

The communications director for Trump's inaugural planning committee, Boris Epshteyn, said they welcomed groups expressing their views in a peaceful and lawful manner.

The planning committee told The New York Times that two to three million supporters would be in attendance, but Geldart said DC's homeland security department estimated a crowd of 800,000 to 900,000 supporters.

The intensive security will continue for a week after the inauguration, as Trump attends various public and private events to celebrate his victory.