On a 27 February backgrounder for note-taking purposes, a senior CentCom officer said the following, based roughly on notes taken:

“There’s an Iranian force presence in Iraq. We have a common goal, and a common interest with the Iranians. We don’t have numbers — they are mainly advisers. They are not working with the Iraqi Army in a condoned way that we know of. That is not occurring.”

Then on March 2, the Wall St Journal reported:

Iran took a leading role in the Iraqi military’s largest offensive yet, throwing drones, heavy weaponry and ground forces into the battle while the U.S. remained on the sidelines.
The operation that began Monday aims to retake Tikrit, best known as the hometown of Saddam Hussein, 80 miles north of the capital Baghdad. In addition to supplying drones, Iran’s powerful Revolutionary Guard force has fighters on the ground with Iraqi units, mostly operating artillery and rocket batteries, according to a U.S. military official. Iraqi Shiite militias closely allied with Iran are also heavily involved.
Iran’s semiofficial Fars news agency reported that Qasem Soleimani, head of the Revolutionary Guard’s overseas unit Quds Force, was on the ground near Tikrit advising commanders.

On the face of these two reports, either CentCom does not know what is going on, or does not want to inform the American public about the extent of Iran’s role in Iraq today. Either way, it’s disturbing news.