Iran warned Monday that American pressure to drop its nuclear program will undermine chances for dialogue on the issue.

Iran?s Foreign Ministry spokesman, Hamid Reza Asefi, told reporters that the language of threats and force over the country?s nuclear policy will not work. He said it would only backfire, and harden the Islamic republic?s position.

U.S. officials have repeatedly accused Iran of trying to develop nuclear weapons and of harboring members of the al-Qaida terrorist network ? charges that Iran denies.

On Sunday, Foreign Minister Kamal Kharazi, speaking to Iranian lawmakers, made a similar plea. He urged the United States to stop what is viewed by Tehran as a concerted campaign of intimidation. He said such pressure will lead nowhere. In fact, he said, it will only radicalize extremist thinking in the Middle East.

But calls for detente are being met in Iran with defiance by Iran?s supreme leader, Ayatollah Ali Khamenei. On Sunday, he accused Washington of pursuing what he called a ?devilish plot? to undermine the Islamic republic.

Iran argues that its nuclear program is for electricity generation and that its uranium enrichment is to provide fuel for reactors, not bombs.

However, the head of the country?s nuclear energy program, Gholamreza Aghazadeh, conceded that Tehran failed to tell the International Atomic Energy Agency that it imported a small quantity of uranium 12 years ago. But he insisted that this does not constitute a violation of the Nuclear Non-Proliferation Treaty.

Inspectors from the International Atomic Energy Agency are currently in Iran, and are expected to issue a report on its nuclear program later this month.

Iran has come under growing pressure to sign an additional protocol to the Non-Proliferation Treaty that would allow energy agency experts to carry out surprise inspection of even undeclared sites.

But Tehran says it will not sign the protocol until Washington drops its sanctions against Iran.