The Kremlin called off the deal last in September citing U.N. sanctions against the Islamic republic over its controversial nuclear program.
"Some people who are under the influence of [the United States] thought that if they unilaterally and illegally cancel some defense agreements that they have with us, it will hurt the Iranian nation," Ahmadinejad said in reference to the missile deal between Moscow and Tehran.
"I want to tell them on your behalf that we consider the deal to still be valid. They should execute it. If they don't, the Iranian people will seek its rights, the losses and the fines on it," he said, cheered on by crowds at a public rally in the northeast city of Bojnourd.
The remarks were Ahmadinejad's first direct reaction to Moscow's decision to cancel the delivery of the S-300 missiles.
Western analysts and officials have long feared that Tehran could reverse engineer the system, turning into an offensive weapon.
Russia scrapped the deal clearly caving into international pressure, five years after the deal had been agreed to with Iran.
It remains unclear how the Islamic republic will proceed and what further action it will take against Russia. Senior military and technology officials have hinted that the Kremlin was preparing to reimburse Iran for the canceled deal.
Military analysts have said that deployment of the S-300 missile system would have created problems in any potential war designs against Iran.
The United States and Israel opposed the sale of the system, which can destroy multiple aircraft and missiles at a range of about 100 miles and altitudes of up to 20 miles. It is able to simultaneously track up to 100 targets.
Washington and some of its allies, including Israel, suspect Iran's civil nuclear energy program is a cover for a secret effort to develop weapons. Iran, though, has repeatedly rebuffed the accusation saying it only wants to enrich uranium to the lower levels used in producing fuel for power plants.
At the public rally, Ahmadinejad said Iran had the capability to defend itself without the S-300 missile system.
"The Iranian nation will stand firm in the face of arrogance, for example the U.S. government. The Iranian people do not need missiles to defend themselves," he said.