Hope is one thing, the reality is another. On Tuesday, about 2 million people gathered in Washington D.C. to celebrate the inauguration of Barack Obama as new U.S, president, hoping he will save the economy, but the Wall Street plunged more than 4 percent in New York.

In his address just after taking the swearing-in oath, Obama admitted that the U.S. was "in the midst of crisis is now well understood," listing war, economy, healthcare, home foreclosures, jobs, energy and other challenges.

"Our economy is badly weakened, a consequence of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age," said the new president.

But Obama assured Americans that although "the challenges we face are real, serious many," and "will not be met easily or in a short span of time," America's goals "will be met."

The new president's words were echoed by Dean Glenn, an entrepreneur from Virginia, who told Xinhua that he is optimistic and believes Obama will save the economy and be great leader.

He said: "The economic crisis is a tough problem, it require some smart person to figure it out, I think he is surrounded himself with some very smart persons."

Glenn, who had never been to inauguration before, said: "Today is a day we look forward to for long time," adding that he believes Obama will bring changes to the U.S.. "We will have a new spirit of cooperation, hopefully a respect of the world."

Witnessing Obama was sworn in as the 44th U.S. president, the first black president in America's history, hundreds of thousands of people, like Glenn, erupted in roars of approval, and cheered in the same tone: "Obama, Obama!"

A recent national poll also showed that Obama's approval rating had risen to nearly 80 percent, revealing people's satisfaction with his work in the transition of power, establishment of his cabinet, as well as high expectations of his administration after Jan. 20.

"I think he (Obama) is going to do a magnificent job, he has several teams that would change the nation," said David S. TorainII, head of Mathematics department of Hampton University, who joined the jubilation near the Washington Monument, which stands at the central of the National Mall.

As for the economy, however, he seemed to be not so optimistic. Inheriting a series of economic problems on a scale not seen since the Great Depression, Obama will have a hard time reviving the nation's sagging economy, he noted.

"It might took long time to get out of the meltdown. I don't think anybody can turn around in next 6 months," he told Xinhua.

But he believed that Obama would help improve the situation. "I think he will be the greatest president since John F. Kennedy, he has great ideas, let's wait and see what happens," he said.

But the Wall Street cannot wait. The U.S. stock market plunged more than 4 percent on Inauguration Day Tuesday as bank woes spread while investors failed to find confidence from President Barack Obama's inauguration speech.

The Dow Jones Industrial Average was down more than 330 points, or 4 percent, falling below 8,000 for the first time in 2009, while the Standard & Poor's 500 and the Nasdaq indexes dropped more than 5 percent.

Editor: Yan