The crisis "represents a threat not only to Iraq but to regional and international peace", Maliki told Washington's top diplomat in Baghdad, a statement from his office said.
Kerry arrived today on a mission to push for Iraqi unity and stability in the face of a major militant offensive that threatens to tear the country apart.
The offensive, led by jihadists from the Islamic State of Iraq and the Levant but also involving other groups, has overrun major areas of five provinces north and west of Baghdad.