The Department of Veterans Affairs is facing a growing backlog of disability claims, fueled by veterans returning from Iraq and Afghanistan and a policy change making it easier for Vietnam veterans to file Agent Orange-related claims.

The number of pending claims before the VA stood at 853,831 on Friday, an increase of nearly 100,000 from last year and nearly 500,000 from three years ago.

“Nearly 1 million veterans today are stuck in the backlog and more than half wait at least half a year to find out if their claim has been processed,” said Rep. Jeff Miller (R-Fla.), chairman of the House Veterans Affairs Committee.

Although the VA has processed nearly a million claims over the past year, another 1.3 million new claims were filed during the same period.

Of the approximately 2.2 million veterans of the wars in Iraq and Afghanistan, 624,000 have filed disability claims and many more are expected. In addition, more than 200,000 Vietnam War veterans have filed claims based on new regulations adopted in 2010 making it easier to get compensation for health problems caused by exposure to defoliants such as Agent Orange.

VA Secretary Eric K. Shinseki launched a department-wide effort to break the backlog, according to agency officials. The budget for the Veterans Benefits Administration reached $2 billion in 2012, a 20 percent increase over the previous year, which the VA says will accelerate services for veterans. But some members of congressional oversight committees question whether there is much to show for the additional money.

The VA is preparing a new paperless claim processing system that officials say will help the department reduce the backlog by taking months out of the process.

“The only way we’re going to be able to do that is . . . to get out of the paper world and into the digital world,” Thomas J. Murphy, director of compensation service for the Veterans Benefits Administration, said at a hearing Tuesday before the House Veterans’ subcommittee on disability assistance and memorial affairs.

The system, which the VA says uses cutting-edge information technology, has been tested in Rhode Island and Utah, and will be rolled out nationwide beginning this summer and continuing through 2013.

The VA also renewed its efforts to reform the complex disability rating system, which has not been comprehensively revised since it was created at the end of World War II.

“No one has managed to find a viable solution . . . since its introduction more than half a century ago,” Miller said.

Members of the subcommittee urged the Defense Department and the VA to standardize their disability rating systems and eliminate confusion between the two.

“The fact of the matter is veterans still don’t have a seamless transition,” said Rep. Jon Runyan, (R-N.J.), chairman of the subcommittee. “Veterans are getting stuck in the system between the bureaucracy of DOD and VA.”

The revision — which began in 2009 and involves a systematic and comprehensive review of current medical information with panels of experts in 15 areas of health, including mental disorders, infectious diseases and the respiratory system — is not expected to be completed until 2016. “This is a process that needs to be done right,” Murphy told the subcommittee.

But veterans service organizations are urging quicker action. “Vets are dying while waiting for the VA to do this job,” Theodore Jarvi, past president of the National Organization of Veterans’ Advocates, told the subcommittee.