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The leading reformist candidate in upcoming Iranian presidential elections said Monday that if elected, he would negotiate with the U.S but that Iran would not give up its nuclear program.

Speaking in his first news conference since declaring his candidacy, Mir Hossein Mousavi said if Barack Obama's administration changes the U.S.'s policies toward Iran, Mousavi would be open to talks. But, in comments that echo other top Iranian officials, Mousavi said the country is still waiting to see how Obama's administration differs from that of his predecessor.

"We will definitely negotiate with them. Why not?" Mousavi said. "Peace with any country would benefit our interests."

The Obama administration has said it wants to engage Iran, a different tactic than that of the Bush administration which sought to isolate the country. But Obama has also said that Iran's nuclear and missile programs pose a threat.

The U.S. and its allies have charged Iran is trying to build nuclear weapons. Iran denies the charge, saying its nuclear program is designed for peaceful purposes such as power generation.

Mousavi said talks with the United States would be beneficial, as long as Iran does not have to "pay heavy costs such as the deprivation of advanced technologies," a reference to Iran's disputed nuclear activities.

"We have to have the technology," Mousavi said, adding that the consequences of giving up the country's nuclear program would be "irreparable" and that the Iranian people support the nuclear program.

Many Iranians across the political spectrum have rallied behind the country's nuclear program which is considered a source of national pride.

Mousavi said he would attempt to "lessen the costs of having the (nuclear) technology," a reference to the fact that Iran is under U.N. sanctions over its refusal to halt its nuclear activity.

Mousavi, 67, is seen by many as the candidate with the best chance of defeating current president, Mahmoud Ahmadinejad, a hard-liner who's often been at odds with the United States.

Mousavi's hard-line past and spotless revolutionary credentials appeal to conservatives. Mousavi's reformist past — he was a senior adviser to former President Mohammad Khatami who served two terms before Ahmadinejad was elected — also appeals to Iranians eager for reform.

Mousavi came to prominence after the 1979 Islamic Revolution that toppled the U.S.-backed shah.

He served briefly as foreign minister, then was prime minister from 1981-1989. His premiership spanned the destructive eight-year war with Iraq, in which at least a million people on both sides were killed.

Mousavi Monday also condemned the killing of Jews in the Holocaust, a much different stance than Ahmadinejad who in 2005 called the Holocaust a myth.

"Some people were killed there, some Jews were killed there, we condemn the killing of a single innocent person," said Mousavi. But he added that the world should not stand by and watch the killing of Palestinian people by Israel.