Caracas , Venezuela ( CNN ) -- Iranian President Mahmoud Ahmadinejad and Venezuelan President Hugo Chavez pledged closer cooperation on Monday , vowing to fight poverty and imperialism . The two leaders signed a series of accords in the areas of industry , science , technology and politics , the state-run AVN news agency reported . Sitting side by side in front of a room full of reporters , they presented a united front in their opposition to the United States . `` It 's clear they are afraid of our development , '' said Ahmadinejad . Earlier , at a welcoming ceremony outside the Venezuelan presidential palace , the Iranian president called Chavez his `` dear brother , '' and said his nation has peaceful intentions . `` Our weapon is logic . Our weapon is culture . Our weapons are human values , '' he said . Chavez pledged to work with his Iranian counterpart to stop the `` imperial insanity '' of the United States , which he described as a `` threat for the world . '' The Venezuelan president mocked concerns from Washington about his country 's relationship with Iran , joking that U.S. media reports made it sound as though he and Ahmadinejad would be launching missiles and bombs at the U.S. capital . `` We are not warmongers , '' Chavez said , as the Iranian president nodded in agreement . `` Iran has not invaded anybody . '' It 's no coincidence that Venezuela is Ahmadinejad 's first stop on a four-nation Latin America tour this week . Despite their cultural differences , Venezuela and Iran have found significant common ground : Both are among the world 's top crude oil exporters , and their leaders are strong allies united by a fierce opposition to what they describe as U.S. imperialism . The Iranian leader arrived in Caracas on Sunday and is traveling with his ministers for foreign affairs , energy and economy , according to IRNA , Iran 's official news agency . Over the years , the two nations have signed more than 270 accords , including trade deals and agreements on construction projects , car and tractor factories , energy initiatives and banking programs . Chavez has also helped the Islamic republic forge relationships with other members of the Bolivarian Alliance of the Americas , an eight-nation regional bloc Chavez founded . Even before he arrived , Ahmadinejad 's plans for a Latin American tour grabbed global attention , as tensions grow between many Western powers and Iran over Tehran 's nuclear program . Officials in the United States and other Western nations have ratcheted up sanctions against Iran several times since a November report by the U.N. nuclear watchdog agency said the Iranian government was developing the technology needed to build a nuclear weapon . Last month , U.S. President Barack Obama announced sanctions against Iran 's central bank . On Monday the United Nations ' nuclear watchdog agency confirmed that uranium enrichment has begun at a nuclear facility in northern Iran . Iran says there 's a medical purpose behind the nuclear program . But in Washington , U.S. State Department spokesman Victoria Nuland said the confirmation that Iran was enriching uranium to `` a level that 's inappropriate '' is `` obviously a problem . '' Not everyone in Venezuela is happy with Ahmadinejad 's visit . Diego Arria , an opposition politician , described the trip as a `` provocation '' to the United States and an embarrassment for Venezuela . `` It comes at the worst moment -- at a time when Ahmadinejad is being looked at by the international community with great fear . ... It 's bringing the threat to the United States closer to home , '' he said . The Iranian president is scheduled to visit Nicaragua , Cuba and Ecuador later this week as part of his five-day tour . CNN 's Catherine E. Shoichet in Atlanta and CNN 's Luis Carlos Velez in Caracas contributed to this report .
Ahmadinejad says his weapons are logic , culture and human values . He refers to Venezuela 's president as his `` dear brother '' Chavez : Venezuela , Iran must stop the `` imperial insanity '' of the United States . The Iranian president is on a four-nation Latin American tour .