CARACAS, Venezuela - President Hugo Chavez urged soldiers on Sunday to prepare for a guerrilla-style war against the United States, saying that Washington is using psychological and economic warfare as part of an unconventional campaign aimed at derailing his government. Dressing in olive green fatigues and a red beret, Chavez spoke inside Tiuna Fort — Venezuela's military nerve-center — before hundreds of uniformed soldiers standing alongside armored vehicles and tanks decorated with banners reading: "Fatherland, Socialism, or Death! We will triumph!" "We must continue developing the resistance war, that's the anti-imperialist weapon. We must think and prepare for the resistance war everyday," said Chavez, who has repeatedly warned that American soldiers could invade Venezuela to seize control of the South American nation's immense oil reserves. U.S. officials reject claims that Washington is considering a military attack. But the U.S. government has expressed concern over what it perceives as a significant arms built-up here. Chavez — a close ally of Cuban leader Fidel Castro — told soldiers the Washington was trying to weaken and divide Venezuelan society, including the armed forces, without resorting to combat. "It's not just armed warfare," said Chavez, a former army officer who is leading what he calls the "Bolivarian Revolution," a socialist movement named after 19th-century independence hero Simon Bolivar. "I'm also referring to psychological warfare, media warfare, political warfare, economic warfare." Under Chavez, Venezuela has recently purchased some $3 billion worth of arms from Russia, including 53 military helicopters, 100,000 Kalashnikov rifles, 24 SU-30 Sukhoi fighter jets. Last week, Chavez said he is considering arms purchases, including submarines and a missile-equipped air defense system, as he prepares for a tour of Russia, Belarus and Iran. "We are strengthening Venezuela's military power precisely to avoid imperial aggressions and assure peace, not to attack anybody," he said Sunday.