Iran and Syria are blasting the United States for providing funds, food and medical supplies to rebels fighting Syrian President Bashar al-Assad.
Secretary of State John Kerry announced this week that, for the first time, the United States would provide non-lethal aid directly to anti-Assad forces.
At a joint press conference in Tehran on Saturday, the Syrian and Iranian foreign ministers called the policy a "double-standard."
Assad's supporters — which include Iran and Russia — describe the uprising as a terrorist campaign.
"I do not understand how the United States can give support to groups that kill the Syrian people," Syrian Foreign Minister Walid al-Moualem said Saturday. "This is nothing but a double-standard policy ... One who seeks a political solution does not punish the Syrian people."
The new U.S. aid is designed to boost the rebels and pave the way for a peaceful political transition. It includes $60 million for opposition groups.
The Syrian civil war has killed 70,000 since it began in 2011, according to Reuters.