Correction: A previous version of this article reported that the number of U.S. troops in Iraq killed by Iranian-backed militants was at least 608, as written in a State Department transcript. However, the correct number is 603, according to a follow-up statement by the Pentagon.

The Pentagon is upping the official estimate on the number of U.S. troops in Iraq who were killed by Iranian-backed militias, now putting that number at at least 603.

Officials previously said that Iran was linked to the deaths of roughly 500 troops.

That means roughly one in every six American combat fatalities in Iraq were attributable to Iran.

The deaths are attributed to proxies sponsored by the Islamic Revolutionary Guard Corps — Iran’s elite military force that protects the regime from internal and external threats.

“During Operation Iraqi Freedom, DoD assessed that at least 603 U.S. personnel deaths in Iraq were the result of Iran-backed militants,” Navy Cmdr. Sean Robertson, a Pentagon spokesman, said in an email.

“These casualties were the result of explosively formed penetrators (EFP), other improvised explosive devices (IED), improvised rocket-assisted munitions (IRAM), rockets, mortars, rocket-propelled grenades (RPG), small-arms, sniper, and other attacks in Iraq," Robertson said.

The Pentagon did not provide Military Times with the new report to independently assess.

The new assessment was given to the State Department and reported to the press during a briefing Tuesday.

“This death toll is in addition to the many thousands of Iraqis killed by the IRGC’s proxies," State Department deputy spokesman Robert Palladino said during the press brief.

That new total accounts for 17 percent of all deaths of U.S. personnel in Iraq from 2003 to 2011, the State Department said.

“That’s a Department of Defense statistic," Palladino added.

Most of the deaths occurred during the surge in Iraq, when President George W. Bush pushed thousands more troops into the country to deal with the sectarian civil war boiling over between Shiite and Sunni groups.

American personnel in Iraq faced off against highly lethal bombs, like the EFPs, which were allegedly manufactured and supplied by Iran to Shiite militias across the border in Iraq.

Lawsuits filed in U.S. District Court in Washington have previously attempted to hold the Iranian government legally accountable for the deaths of Americans that died from these weapon systems.