Huge crowds gather for Obama's date with history

By Jeff Mason and Ross Colvin

WASHINGTON (Reuters) - Barack Obama prepared to make history on Tuesday as the first black U.S. president, riding a wave of hope in America and the world as he tackles the worst economic crisis in 70 years and two wars.

Hundreds of thousands of people, bundled up against the cold and in a festive mood, packed Washington's Mall, which stretches 2 miles (3 km) from the Capitol to the Lincoln Memorial on the Potomac River, and along Pennsylvania Avenue to the White House.

People lining the streets cheered wildly as a motorcade carrying Obama, his wife Michelle, and President George W. Bush and his wife Laura, made its way to the Capitol from the White House.

Obama, a Democrat, was due to be sworn in on the steps of the Capitol as the 44th U.S. president just before noon EST (1700 GMT), taking over from Bush, a Republican.

The inauguration was taking place amid unprecedented security. About 8,000 police were deployed and a total of 32,000 military personnel were on duty or on standby.

The Homeland Security Department said authorities were investigating a potential threat of "uncertain credibility" in connection with the inauguration.

This will be the first inauguration of a new U.S. president since the Sept. 11, 2001, attacks that took place early in Bush's two-term presidency and deeply shaped his policies, prompting Washington's war on terrorism. Obama's election has also stirred white supremacists to anger, sparked arrests during his campaign and raised assassination fears.

Major U.S. stock indexes fell on Tuesday on mounting worries over grim earnings and the health of the banking sector, highlighting the scale of the financial problems Obama will face.