ERBIL, Iraq -- U.S. Secretary of Defense Ash Carter told CBS News on Thursday that in spite being "warned by lots of people along the way" to be cautious with his communications after assuming the top job at the Pentagon, he continued to send work emails from his iPhone "until a few months ago."

Carter told CBS News correspondent Charlie D'Agata in an interview at an American base in Erbil, northern Iraq, that he never sent anything classified via his personal account, but that he did "occasionally" send "administrative" emails to his "immediate staff."

"It's a mistake, and it's entirely my own," the secretary told D'Agata, saying that as soon as it became clear to him that the practice was against policy, "I stopped."

He said he generally doesn't use email to communicate much.

The revelation that Carter had sent work emails from a personal account was first published Wednesday by the New York Times.

It quickly made headlines in the wake of the recent scandal involving Democratic presidential candidate Hillary Clinton's use of a personal account to send work emails during her time as Secretary of State.

Carter conceded to D'Agata that the attention Clinton had received -- which involved multiple grillings by lawmakers on Capitol Hill, was "more reason why I should have been" careful to follow communications protocols, "and that's my fault."

"I have to hold myself to strict standards," he told CBS News, "and I didn't in this case."

On the ISIS fight

The defense chief flew to Erbil, the capital of Kurdish territory in northern Iraq, to meet U.S. and Kurdish commanders at the spear-tip of the battle to defeat the Islamic State of Iraq and Syria (ISIS), which Carter said confidently, "we'll win."

"I don't have any question about that," he told D'Agata. "But we want to win faster."

Carter said President Obama wanted to "accelerate" the effort to squeeze ISIS in it's two strongholds; the group's self-declared capital in Raqqa, Syria, and Iraq's second-largest city, Mosul.

D'Agata said that what he saw in Syria in recent days with the Kurdish forces who are receiving U.S. backing, was "chaos." Infighting between rival groups in Syria is complicating the U.S. effort to get them to focus on pushing ISIS back toward Raqqa.

Kurdish commanders have told D'Agata they're grateful for the addition of U.S. Special Operations forces to the battle, and it has given them new hope that the fight can be won. But they also said they still need heavier weapons to beat ISIS and that any additional U.S. troops would be welcomed.

Pushed by D'Agata on constant requests he heard from the Kurdish commanders for heavier weapons, Carter stressed that the U.S. and it's allies, such as Germany, have already contributed significant hardware, but that a big part of the reason he was in Erbil was to discuss further needs.

"They've asked especially for ams, and we've provided arms," Carter said, adding that if the Kurds are able to "continue to move south" toward ISIS' headquarters in Raqqa, "we'll continue to do that."

"We're going to take Raqqa, and that's how we're going to do it," he said.