WASHINGTON - Barack Obama on Wednesday will mark the 100th day of his presidency after a whirlwind start in which he has signaled a new approach on policies from the economy to climate change to U.S. relations with Iran.

Some have used the milestone to assess Obama's policies, even as analysts cautioned it was too soon to say whether his long list of initiatives will yield success.

While dismissing the 100-day milestone as an artificial gauge created by the media, the White House is nonetheless putting a spotlight on it with high-profile events.

Those include a visit by Obama to Arnold, Missouri, near St. Louis, for a town-hall style event and a televised news conference at the White House at 8 p.m. EDT/0000 GMT.

The popular U.S. president, whose approval ratings are above 60 percent, will likely use the events to push his agenda for overhauling health care, fixing the troubled banking sector, rescuing U.S. automobile companies, combating global warming and pursuing greater engagement abroad.

Looming large as well for Obama is a flu outbreak that has presented him with his first public health emergency and a simmering controversy over his decision to release classified documents detailing harsh interrogations of terrorism suspects during the Bush administration.

The tradition of marking the first 100 days of U.S. presidencies dates back to Franklin Delano Roosevelt, who trumpeted his ability to push through 15 pieces of major legislation in that time period after taking office in 1933 in the midst of the Great Depression.

Though none of Roosevelt's successors have yet matched the activity of his first few months in the White House, there remains a fascination in the media with the gauge.

There is no magic to the first 100 days, said Ross Baker, a political science professor at Rutgers University. I think people are always looking for a maker or some sort of guidepost.

As an example of the measures's flaws as a leading indicator, many analysts cite the first 100 days of the presidency of George W. Bush.

The Republican president's two terms in office came to be defined by decisions such as the launch of the Iraq war that occurred in the aftermath of the September 11, 2001, attacks -- nearly nine months after Bush took office.

STIMULUS, WAR STRATEGIES, HEALTH CARE

Still, Baker and other experts said Obama's early months have revealed much about his style of governing, including his calm demeanor and effectiveness at commanding the stage but also his penchant for piling a lot onto his policy plate.

So far in his presidency, Obama has enacted a $787 billion stimulus program, launched a drive to overhaul the health care system, made overtures toward longtime U.S. foes Iran and Cuba and unveiled new strategies for the Iraq and Afghanistan wars.

William Galston, a scholar at the Brookings Institution and a former adviser to President Bill Clinton, said he viewed the 100-day mark as an entirely artificial benchmark.

On the other hand, Galston said, I think we've learned a fair amount about Obama the human being occupying the Oval Office.

But a lot of people are leaping from the fact that he's set an enormous number of things in motion to the conclusion that those things that are now in motion are necessarily going to reach the finish line, Galston said. It's not a leap I'm prepared to take.

On the domestic policy side, Obama has been criticized by some who contend the stimulus package and a proposed $3.55 trillion budget he laid out for 2010 will curb economic growth in the future by leading to a pileup of government debt.

Some critics have also faulted Obama's handling of the banking crisis, saying he should have moved earlier and more aggressively to try to grapple with problem of bad debt hanging over the financial system.

But Obama's supporters point to what they see as early signs his economic remedies may be working, including a steadier tone to the stock market and a stabilization of new claims for jobless benefits after their prior huge increases.

The president also got some upbeat news on the political front this week with the defection of Pennsylvania Senator Arlen Specter from the Republican Party.

Specter's decision to join Obama's Democrats may put the president's party within reach of a crucial 60-seat majority in the Senate. That could make it easier for Obama to pass some of his top initiatives such as health care reform.

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