(CNN) -- Venezuelan President Hugo Chavez Sunday said his country will stop exporting oil to the United States if there is a military attack stemming from escalating tensions between Venezuela and Colombia.

Speaking at a political rally, Chavez warned of a military attack from Colombia, and accused the United States of being behind such an attack.

"The Yankee empire has no limit to its manipulation," Chavez said.

Colombia and Venezuela are at odds over accusations that Colombian rebels have found refuge in Venezuela. Colombia called an emergency meeting of the Organization of American States last week, in which it provided photos that it said were evidence of camps belonging to the Revolutionary Armed Forces of Colombia -- known by its Spanish abbreviation, FARC -- in Venezuela.

Venezuela denies the accusations, and in response broke off diplomatic ties with the neighboring country.

If there is an attack from Colombia, Chavez said Sunday, Venezuela would stop supplying oil to the United States, "even if we have to eat rocks" because of the repercussions.

"That would be a response of dignity and high caliber," Chavez said.

According to the U.S. Energy Information Administration, Venezuela is the fifth-largest supplier of crude oil to the United States, delivering an average of 894,000 barrels of oil per day.

He also warned there would be "internal measures" in Venezuela against the opposition and media in case of a war. He accused opposition governors of being in contact with the Colombian military.

Chavez said Venezuela rejected the possibility of any foreign guerrilla or paramilitary group to operate in his country.

Colombia has accused Chavez of supporting the rebels, and Chavez has said Colombian officials and right-wing paramilitary units have plotted his assassination.

Security analysts say FARC guerrillas operate mostly in Colombia but have carried out extortion, kidnappings and other activities in Venezuela, Panama and Ecuador.

FARC is said to traffic in cocaine to finance its insurgency.

Colombia has also accused another neighbor, Ecuador, of giving refuge to rebels. In 2008, Colombia carried out a raid in Ecuadorian territory that resulted in the killing of a top FARC leader.

Last week was not the first time Chavez cut off diplomatic ties with Colombia.

A year ago, Chavez "froze" the nations' relationship over Colombian accusations that Venezuelan weapons had made it into the hands of rebels.

Colombia said it had evidence that shoulder-fired anti-tank weapons recovered from FARC guerrillas were of Venezuelan origin. Venezuela denied the allegations and said the rebels may have stolen the weapons from a Venezuelan base.