According to U.S. officials, Iran has been secretly sending surveillance drones over Iraq to help Shiite militias battle ISIS militants. The officials also said Iran has been supplying Iraq with up to 140 tons of military equipment per day.

"It's a substantial amount," said a senior U.S. official told The New York Times. "It's not necessarily heavy weaponry, but it is not just light arms and ammunition."

While Iraqi forces need all the help they can get — ISIS has been capturing city after city and promises to take Baghdad — Iran's involvement could ultimately escalate the conflict.

In a news conference yesterday, Secretary of State John Kerry noted with concern that the war in Iraq is being "widened." He said, "From our point of view, we've made it clear to everyone in the region that we don't need anything to take place that might exacerbate the sectarian divisions that are already at a heightened level of tension."

Syria has also entered into the conflict — Syrian warplanes have targeted ISIS militants in Iraq at least twice this week. And the Associated Press reports that Jordan, Kuwait, Saudi Arabia, and Turkey are all "bolstering flights" just inside Iraqi airspace to monitor the conflict. The U.S. currently has 300 military advisers in Iraq helping troops with strategy and intelligence.

Kerry has been pushing Iraq to form an inclusive, multi-sectarian government so it can guard against "outside forces moving to fill a vacuum." Prime Minister Nouri al-Maliki has so far rejected calls to step down and put an interim government in place.

[Image via AP]