UPDATE 1-Three former U.S. SEC chairmen endorse Obama

(Adds quotes, background, previous dateline SOUTHFIELD)

By Jeff Mason

WARREN, Mich, May 14 (Reuters) - Three former chairmen of the U.S. Securities and Exchange Commission endorsed Democratic presidential candidate Barack Obama on Wednesday, bolstering the Illinois senator's economic credentials and bipartisan appeal as he closes in on his party's nomination.

Former SEC head William Donaldson, who was appointed by Republican President George W. Bush, joined Arthur Levitt and David Ruder in backing Obama, who leads rival Hillary Clinton in the number of delegates necessary to become the Democratic White House nominee.

Levitt was appointed by former President Bill Clinton, a Democrat, while Ruder was appointed by former President Ronald Reagan, a Republican.

All three commended Obama for his approach to regulation.

"Each of us has been committed to prudent economic policy and effective financial regulation for many years," they said in a joint statement along with former Federal Reserve Chairman Paul Volcker, also an Obama supporter.

"We believe Senator Obama can provide the positive leadership and judgment needed to take us to a stronger and more secure economic future."

In the statement they praised Obama's "reasoned approach" in analyzing "the current financial crisis and the need for balanced regulatory reform."