The statement comes on the day when the deadline set by the UN Security Council for Iran to halt its uranium enrichment expires.
"The Islamic Republic of Iran will continue to move down the path of achieving successes in the nuclear sector, and we will not budge an inch," Mahmoud Ahmadinejad said.
Iran has consistently rejected suspicions that it seeks nuclear weapons, saying it only wants nuclear fuel for energy generation, which is in line with the Nuclear Non-Proliferation Treaty (NPT).
"Those opposing Iran's intention to develop peaceful nuclear technologies know full well that if we overcome this barrier, other nations will start developing civilian nuclear energy, and they [the opposing side] will not be able to continue acting selfishly," the president said.
In December, the UN Security Council imposed sanctions on Iran, banning sensitive technology transfers to and restricting financial transactions with the country.
The issue will return to the Security Council, where the U.S. is expected to push for more sanctions, following a report by International Atomic Energy Agency head Mohamed ElBaradei.
Further sanctions could result in a complete or partial severing of economic, diplomatic and other ties with Iran.
Russia and China, key economic partners of Iran and veto-wielding Security Council members, which have been opposed to drastic measures against Tehran, are advocating diplomacy.