The U.S. military has revealed it believes Iran has helped kill more than 600 U.S. troops in Iraq since 2003, according to newly revealed and formerly-classified numbers.

"In Iraq, I can announce today, based on declassified U.S. military reports, that Iran is responsible for the deaths of at least 608 American service members," Brian Hook, U.S. Special Representative for Iran, said during a State Department briefing Tuesday. A Pentagon spokesman told the Washington Examiner the number of troops killed is "at least 603."

“This accounts for 17 percent of all deaths of U.S. personnel in Iraq from 2003 to 2011. This death toll is in addition to the many thousands of Iraqis killed by the IRGC’s proxies.” Since 2003, more than 4,400 U.S. service members have been killed in Iraq.

This number has been a matter of debate for years, shrouded in secrecy by the Pentagon with the previous estimate put at about 500. Scores of American personnel were killed by highly lethal bombs, known as explosively formed projectiles, or EFPs, that Iran manufactured and supplied to Shiite militias across the border in Iraq. Many EFPs were powerful enough to destroy U.S. Humvees and even breach tank hulls.

In July 2015, during the Senate Armed Services Committee confirmation hearing for Marine Corps Gen. Joseph Dunford, now chairman of the Joint Chiefs of Staff, Sen. Tom Cotton, R-Ark., pressed him on this. “You have served in Iraq and Afghanistan. Do you know how many soldiers and Marines underneath your command were killed by Iranian activities?” Cotton asked.

“Senator, I know the total number of soldiers, sailors, airmen, and Marines that were killed by Iranian activities, and the number has been recently reported as about 500," Dunford replied. "We were not always able to attribute the casualties that we had to Iranian activity, although many times we suspected it was Iranian activity, even though we did not necessarily have the forensics to support that.”

Cotton replied: “So about 500 confirmed, but many more suspected killed in action and even more wounded in action."

In August 2015, at a hearing with then-Secretary of Defense Ash Carter in front of the Senate Armed Services Committee, Sen. Ted Cruz, R-Texas, pushed the Pentagon to make the numbers public. “I understand that the Joint Personnel Recovery Agency has a classified list of roughly 500 American soldiers … I would ask, Secretary Carter … that the Defense Department release that list to every member of this committee, declassify that list and release it directly to the service members' families who were murdered by [Iranian] General Soleimani," Cruz said.

Qasem Soleimani, 62, is a major general in the IRGC. Since 1998, he has been commander of its Quds Force, a division primarily responsible for overseas military and clandestine operations.

U.S. Central Command spokeswoman Maj. Genieve David echoed the estimate of 500 Americans killed in September 2015. “It is important to understand that the CENTCOM statistics on EFP [explosively formed penetrator] detonations are a subset of all the Iranian activities estimated to have killed approximately 500 U.S. troops in Iraq during OIF [Operation Iraqi Freedom]," David said.

The newly declassified number provided by the State Department, holding Iran responsible for the deaths of 608 U.S. service members in Iraq, is more than one hundred deaths higher than the previous estimate.

During Tuesday’s State Department press briefing, Hook also gave an update on the U.S. government’s ramped-up efforts to confront the Iranian regime. “Since taking office, the administration has designated over 970 Iranian entities and individuals. The sanctions announced last week against front companies supporting the Islamic Revolutionary Guard Corps and Iran’s ministry of defense were the 26th round of American sanctions," Hook said. "Our sanctions have targeted a range of threats, especially Iran’s support of terrorism, missile proliferation, its nuclear program, human rights abuses, and others.”

Hook said the U.S. had placed sanctions against more than 70 financial institutions linked to Iran, targeted the oil shipping networks that Iran was illicitly using to fund its ally Assad and its proxy Hezbollah, and visited over 50 different countries to warn against doing business in Iran.

Hook also condemned Iran’s involvement in conflicts in Yemen, Syria, and Lebanon, stating that “the effects of Iran’s meddling had been felt most sharply by the region’s innocent civilians.”

Hook said nearly a year after the U.S. withdrew from the Joint Comprehensive Plan of Action, also known as the Iran Deal, the actions that the Trump administration has taken since then have helped contain Iran’s activities, including its ability to fund terrorism and to prop up its allies and proxies in the region.

“As we have done from the start, we will continue to call on all nations to join us in restoring the basic demands on Iran to behave like a peaceful nation. This includes ending its pursuit of nuclear weapons, stop testing and proliferating ballistic missiles, stop sponsoring terrorist proxies, and halt the arbitrary detention of dual citizens,” Hook said.