CARACAS, Venezuela (AP) Venezuela has no interest in talking directly to Colombia to end a monthslong crisis but would support an effort by other South American nations to broker a solution, a top government official said Sunday.

Deputy Foreign Minister Francisco Arias Cardenas said tensions between Caracas and Bogota should be taken up by the Union of South American Nations, a 12-member organization known as Unasur.

Any mediation efforts aimed at easing ongoing tensions between Colombia and Venezuela ''must be done within the heart of Unasur,'' Arias Cardenas said during a televised interview.

The diplomat spoke a day after President Hugo Chavez urged civilians to join government-organized militias to be ready to defend Venezuela from a foreign invasion. He said he thinks ''it's the obligation'' of every member of his socialist party to participate in an ongoing effort to organize combat groups.

Chavez, a former paratroop commander, said the 300 armored vehicles and Russian war tanks that are due to arrive in Venezuela soon along with radar and air defense systems, will help the country's military expand its operational capacity.

Venezuela has already bought more than $4 billion worth of Russian arms since 2005, including 24 Sukhoi fighter jets, dozens of attack helicopters and 100,000 Kalashnikov assault rifles. And in September, Russia opened a $2.2 billion line of credit for Venezuela to purchase more weapons.

The military acquisitions, coupled with weapons purchases among South American nations including Brazil and Ecuador, have raised concerns of an arms race in the region.

Venezuela must prepare for a possible armed conflict, Chavez said, because the United States and Colombia could attack. He claims U.S. ''imperialists'' want to undermine his ''Bolivarian Revolution,'' a political movement named after 19th-century independence hero Simon Bolivar.

He vehemently denied that Venezuela plans to attack its neighbor.

Venezuela and Colombia have been feuding for months over the agreement between Bogota and Washington allowing the U.S. military to increase its presence at seven Colombian bases under a 10-year lease agreement.

Colombian and U.S. officials say the deal is necessary to more effectively help Colombia fight drug traffickers and leftist rebels, but Chavez claims the agreement poses a threat to Venezuela.

''We are the No. 1 target on the imperial map of this continent,'' he said.