By Idrees Ali

WASHINGTON (Reuters) - Officials in the U.S. military's Central Command, which oversees combat operations in the Middle East and South Asia, were much more likely than counterparts elsewhere to believe superiors distorted or suppressed their analyses, according to a government intelligence survey.

Results of the December 2015 survey are likely to reinforce questions in Congress and elsewhere about whether the administration is pressuring officials to make over-optimistic claims about progress against Islamic State and the Taliban to help U.S. President Barack Obama leave office in January on a high note.

The Office of the Director of National Intelligence (ODNI) survey, which had not been reported until now, was one of the main topics of a House intelligence committee hearing on Thursday.

In one of its more striking findings, only 36 percent of Central Command officials surveyed said they were confident that their mid- and senior-level managers were not deliberately distorting or suppressing their analyses.

The average for the other eight U.S. military commands, which include those in the Pacific, Africa and Europe, was 72 percent.

Central Command directs the American military missions in Afghanistan, Iraq, Syria and elsewhere in the Middle East and South Asia. Its analysts typically assess intelligence such as potential targets for bombing and an enemy's strength.

Asked if "anyone attempted to distort or suppress analysis on which you were working in the face of persuasive evidence," 40 percent of the CENTCOM respondents said yes, compared to an average of 13 percent.

The survey found that when that question was asked, 65 percent of the command's respondents said "politicization" was an issue.

"The data suggests respondents from Central Command believe their workplace adheres to objectivity standards relatively less than do workplaces of their IC counterparts," the report said, using an acronym for the U.S. intelligence community.

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Outgoing Director of National Intelligence James Clapper said the situation at Central Command had improved in the 2016 survey. Clapper told a congressional intelligence hearing on Thursday that CENTCOM objectivity numbers were now similar to those in other combatant commands.

"I do think there is, by virtue of the change in commanders and...(there) has been a change in the atmosphere there and so I've been encouraged by the trends particularly this year," Clapper said.

CENTCOM did not immediately respond to a request for comment. Separately, Clapper told the hearing that he had submitted his letter of resignation but would stay until the end of the Obama administration.

The survey has been conducted annually since 2006 and about 4,000 analysts and managers responded to it, including 125 CENTCOM analysts and managers. It cautions, however, that because responses were voluntary, "care should be taken when broadly interpreting results" for each command.

Officials in other U.S. intelligence agencies said the Central Command issues were not the product of pressure from White House or other senior officials, and played a minor role in the administration's public claims of progress against Islamic State and the Taliban, many of which have proved to be overly optimistic.

That is true, these officials said, because much of the Central Command analysis consists of daily bomb damage assessments and other situation reports, not strategic intelligence, and constitutes only a small part of the material that finds its way from numerous other intelligence agencies, including the CIA and the National Security Agency, into the President's daily intelligence briefing.

Nevertheless, the findings of the survey, which was posted with no notice last month on a remote part of the ODNI website, are likely to raise questions about intelligence assessments provided by Central Command.

Earlier this year, a U.S. congressional report said Central Command painted too rosy a picture of the fight against Islamic State in 2014 and 2015 compared with the reality on the ground and grimmer assessments by other analysts.

The Defense Department Inspector General is investigating the findings and is expected to issue a separate report, military officials said.

(Reporting by Idrees Ali; Editing by Simon Cameron-Moore and Alistair Bell)