Venezuelan President Hugo Chavez ordered his military on Sunday to prepare for a possible armed conflict with Colombia while accusing the United States of trying to provoke a war between the South American neighbours.

"The best way to avoid war is preparing for it," Chavez told military officers during his weekly television and radio program.

"The empire is more threatening than ever," he said, referring to the U.S. "Don't make a mistake, Mr. Obama, by ordering an attack against Venezuela by way of Colombia."

Chavez has criticized a recent agreement between the U.S. and Colombia that would give U.S. troops greater access to Colombian military bases, calling it a threat to regional stability.

The two pact-signing countries say the deal is necessary to fight the war on drugs and a decades-old insurgency in Colombia. Militants often use Venezuela's border region as a haven to resupply and treat their wounded.

There was no immediate reaction from either the Colombian or U.S. government to Chavez's latest remarks.

Tensions along the Venezuela-Colombia border have been exacerbated in recent weeks by a series of shootings and slayings.

Four men on motorcycles shot and killed two Venezuelan National Guard troops at a checkpoint near the border, prompting Venezuela to temporarily close some border crossings.

Venezuela also sent 15,000 soldiers to the border on Thursday, saying it was necessary to increase security.

With files from The Associated Press