Texas Gov. Rick Perry says it's not wise to speculate about what caused an explosion and massive oil spill in the Gulf of Mexico. And he's defending his use of the term "act of God" to describe the disaster.

Perry said Tuesday the phrase is a legal definition and that his point is "nobody knows what happened" at the oil rig off the Louisiana coast. The undersea well has been spewing 200,000 gallons of oil a day.

The governor also cautioned against a "knee jerk" reaction to stop all oil drilling because of the spill.

Perry was planning to be on a conference call Tuesday with Homeland Security Secretary Janet Napolitano and other coastal governors to discuss the spill, which has not reached Texas' shores.