By Patrick Rucker

WASHINGTON (Reuters) - Exxon Mobil Corp has not shared information about its U.S. taxes with a global transparency effort that the company has endorsed and that President Barack Obama has backed, the project's organizers said on Wednesday.

Exxon was one of several energy companies that failed to share U.S.-specific tax information for a report released on Wednesday by the Extractive Industries Transparency Initiative (EITI), which audits payments made by companies for drilling or mining.

EITI is a watchdog group that targets corruption in energy and mineral-rich nations with impoverished populations.

Obama in 2011 committed the United States to the effort, saying it would help ensure "that taxpayers receive every dollar they're due." The president's commitment came while endorsing the Open Government Partnership, an even broader good-government effort conceived that same year.

Exxon<XOM.N>, one of the world's largest corporations, has a seat on the EITI board and has pledged to disclose payments it makes around the world.

The company discloses tax and royalty information in many countries but will not say what it pays the Internal Revenue Service, according to EITI findings released on Wednesday.

Exxon did not report its U.S. federal corporate income tax payments for 2013, the year under review, according to the EITI. Exxon spokesman William F. Holbrook said the company had no comment on the EITI initiative while that "work is still in progress." He said Exxon is "one of the largest taxpayers in the U.S. and around the world."

U.S. corporations are not legally required to disclose their U.S. federal income tax payments publicly and most do not. But they do routinely disclose their global effective tax rates and other accounting.

Under the EITI protocol, however, energy companies that participate, including Exxon, commit to disclosing meaningful payments they make to governments.

Exxon and other EITI participants are expected later this month to formally endorse Wednesday's report.

ConocoPhillips <COP.N>, Chevron Corp <CVX.N> and Continental Resources Inc <CLR.N> are among other major energy companies that did not share tax information with EITI.

ConocoPhillips supports EITI and "has volunteered to make disclosures that it deems appropriate," a spokesman said.

Chevron and Continental did not immediately respond to a request for comment.

The U.S. corporate income tax rate is 35 percent but few multinational companies pay that rate thanks to regulations that allow them to reduce their U.S. tax burdens.

(Editing by Kevin Drawbaugh and Bill Trott)