Ahmadinejad threatened unspecified retaliation by Iran if Europe followed in the footsteps of the United States, which last week announced sanctions against the Islamic state.
"If they plan to cooperate with the enemy of the Iranian nation, we cannot interpret this as a friendly behavior. We will show reaction," the radio quoted Ahmadinejad as saying.
The U.S. measure bans dealings with a host of companies connected to Iran's Revolutionary Guards, an elite force that has extensive business holdings in oil, construction and other sectors.
It also prohibits American companies from working with the Guards-linked Iranian companies and puts pressure on international firms and banks not to deal with them as well.
The U.S. and some of its allies claim Iran's controversial nuclear program masks attempts to produce a nuclear weapon. Tehran denies it is seeking nuclear arms and maintains its uranium enrichment program aims only to produce electricity.
Ahmadinejad spoke after a ceremony inaugurating a petrochemical complex in the southern port of Asalouyeh, some 1,500 kilometers (940 miles) south of the capital, Tehran.
"You, Europeans, know well what will happen in the economic sphere if Iran takes a serious move in this matter," the Iranian leader said.
IRNA, the state official news agency, also quoted Ahmdinejad as saying: "You, Europe, need us more" - a veiled reference to business ties between Tehran and European nations.
According to official statistics Europe is Iran's largest trading partner, with over 40 percent of Iran's imports coming from European Union countries. Also, many European energy companies have been working in Iran's attractive energy market, which is the second oil producer among OPEC countries.
Ahmadinejad also spoke against a new, third round of U.N. sanctions on Tehran which the United States and some of its allies have been pressing for, saying that "enemies of Iran should know that the era of unanimous (U.N.) resolutions against Iranian nation has passed."
Iran is counting on international support from Russia and China - permanent U.N. Security Council members - to prevent harsher U.N. sanctions. The U.N. has imposed two rounds of limited sanctions for Iran's refusal to suspend uranium enrichment, a process which can be used for both nuclear fuel for electricity power plant and weapon.
Russia and China have resisted a third round of sanctions.
IRNA said Ahmadinejad called sanction against his country a "ridiculous story."
The Iranian president's comments came a day after the head of the Revolutionary Guards warned the U.S. against attacking the Islamic Republic, saying if it did, Washington would be "stuck in a quagmire" worse than Iraq or Afghanistan.
Mohammad Ali Jafari, the Guards commander, said Wednesday his forces were prepared to strike back with a "crushing response" if attacked, according to the semiofficial Fars news agency.
Concerns have been mounting in recent months that the United States might attack to prevent Iran from developing atomic bombs. The U.S. has said it is trying to resolve its disputes with Iran diplomatically but also says it has not ruled out any options.