Mexico said it will withdraw its ambassador and sever diplomatic ties with Venezuela if that country's president doesn't apologize Monday for warning Mexican leader Vicente Fox: "Don't mess with me."

In a late-night statement Sunday, Mexico's Foreign Relations Department said that because Hugo Chavez's comments "strike at the dignity of the Mexican people and government, Mexico demands a formal apology from Venezuela's government."

Tensions between Fox and Chavez spilled over after this month's Summit of the Americas in Argentina, where Fox sought to defend a U.S.-backed proposal for a free trade zone while Chavez proclaimed the idea dead.

"President Fox left bleeding from his wound," Chavez said Sunday during his weekly radio and TV show, echoing remarks last week in which he accused Fox of being a "puppy" of the U.S. government for supporting its plans for the Free Trade Area of the Americas.

Chavez recalled a folk song from Venezuela's cattle-raising plains about a thorn, saying it seems appropriate for Fox since "you're a man of horses." After reciting the lyrics, Chavez said: "Don't mess with me, sir, because you'll come out pricked."

Mexico responded within hours, saying a failure to apologize would force it to "ask for the immediate withdrawal of Venezuela's ambassador and a recall of the Mexican ambassador in that country."