Iran's top nuclear negotiator Saeed Jalili blamed the United States for a cyberattack on what he insisted is a nuclear energy -- not weapons -- program, in an interview broadcast Monday.

Days ahead of a high-profile talks over the Islamic republic's nuclear program later this week, Saeed Jalili told NBC News an Iranian investigation found the United States was involved in a cyberattack that apparently shut down a fifth of Iran's nuclear centrifuges in November.

"I have witnessed some documents that show... their satisfaction in that" the United States participated in the cyberattack -- using the Stuxnet computer worm -- that also helped delay Iran's ability to make its first nuclear weapons.

But he said the effort did not wreak as much damage as some media have reported.

"Those who have done that could see now that they were not successful in that and we are following our success," Jalili said, warning the United States was "also weak and vulnerable" to cyberattacks.

His comments came after The New York Times reported over the weekend that US and Israeli intelligence services collaborated to develop the destructive computer worm in a bid to sabotage Iran's efforts to make a nuclear bomb.

Tehran has also blamed its enemies for the killing of three top nuclear scientists last year, and on Monday, it vowed to sue its archfoe Israel for the murder of one of them -- Masoud Ali Mohammadi.

Iran accuses the intelligence services of Israel, the United States and Britain of being behind bomb attacks against the other two nuclear scientists on November 26.

"We believe that there is a meaningful relation between the UN Security Council resolution (sanctioning Iran over its nuclear program) and these kind of activities," Jalili said of the attacks.

"It is a big question for the international community, and a big kind of question in that the name of the scientists of a country mentioned in the United Nations council resolution and then following that the terrorists assassinated them."

But the senior negotiator expressed optimism that despite the acrimony, progress could be made at the second round of talks between Tehran and six world powers due to get underway on Saturday in Istanbul.

"The Islamic Republic of Iran is for talk around and on common points... which are accepted by both sides," he said. "Therefore we are ready to talk for whatever is important from folks."

Jalili dismissed sanctions by the UN, European Union, US and other countries as "something for the old times" that did not have a significant impact and indicated Iran would seek to get them removed at the forthcoming talks.

"It's a kind of indication of frustration... and with this view in mind, we have invited them to return to the negotiation talks," he said.

"We believe that putting aside the wrong approaches and attitudes and adopting and choosing the approach of interacting and engagement with people is the best way to go."

Both the United States and Israel have recently announced however that they believe the program has been set back by several years. US Secretary of State Hillary Clinton pointed to the series of sanctions imposed since June 2009 by the UN Security Council and individual countries.

And Moshe Yaalon, Israel's strategic affairs minister and former military chief, said last month that a series of "technological challenges and difficulties" meant Tehran was still about three years away from being able to build nuclear weapons.

Israel has backed US-led efforts to prevent Iran from developing a nuclear weapons capability through sanctions, but has also refused to rule out military force.

Jalili said Iran will not bow to international demands to halt its uranium enrichment activities -- a process vital to producing a nuclear bomb -- and said Iran's plans for producing 20 percent enriched uranium were aimed solely at "covering our need for medication and isotopes to treat cancer patients.

"We frankly and bluntly mentioned that nuclear weapons are illegitimate and inefficient and they could not help those countries that have the nuclear weapons," he added, blasting nuclear powers as "backwater nations" incapable of solving their own problems.

"They are illegitimate and against humanity."