TEHRAN (Reuters)

Iran has sent a protest letter to the United States accusing it of spying on the Islamic state's nuclear activities, the official IRNA news agency reported on Saturday, citing the country's foreign minister.

The letter, submitted to the Swiss embassy in Tehran which handles U.S. interests in the country, was in reaction to a U.S. intelligence report published last Monday which said Iran halted its nuclear weapons program in 2003.

"The ministry submitted a letter to the Swiss embassy in Tehran ... demanding explanations over America's espionage on Iran's nuclear case," Foreign Minister Manouchehr Mottaki was quoted as saying by IRNA.

He said the report itself had made clear the use of surveillance satellites and other espionage operations and added that "Iran is seriously following up the issue of espionage.

Iranian President Mahmoud Ahmadinejad on Wednesday declared victory over the United States following the release of the report, which contradicted the Bush administration's charges that Tehran was actively seeking a nuclear weapon.

U.S. President George W. Bush has said Iran remained a danger because it was mastering technology with a military use.

But the intelligence assessment appeared likely to increase resistance from Russia and China to U.S. demands for further United Nations sanctions against Iran, following two rounds of U.N. punitive measures since December.

Analysts have also said the U.S. report, which reversed previous assessments, makes it much less likely that the United States would attack Iran.

Iran says its atomic work was always peaceful and aimed at generating electricity so that the world's fourth-largest oil producer can export more of its oil and gas.

Mottaki said the U.S. report to 70 percent reflected "the realities of Iran's peaceful nuclear activities," IRNA reported. Mehr news agency quoted him as saying the other 30 percent related to activities before 2003 and was "all lies."

U.S. Defense Secretary Robert Gates said in Bahrain on Saturday that Iran still poses a threat, arguing it has the capability to restart its weapons program.
Gates also defended Israel's nuclear program, saying the Jewish state did not seek to destroy its neighbors or support terrorism, unlike Iran.

The Swiss embassy represents U.S. interests in Iran because Washington has not had a mission there since 1980, when Iranian students seized the U.S. embassy and held 52 American hostages for 444 days.

In May, Iran's Foreign Ministry summoned the Swiss ambassador to Tehran to condemn what it said was U.S. backing of spy networks inside the Islamic Republic.