Iran’s Supreme Leader Ayatollah Khamenei and Iranian President Mahmoud Rouhani on the 28th respectively expressed their views on the death of an Iranian nuclear physicist in an attack the day before. Khamenei said the perpetrators of terrorist crimes should be punished. < / P > < p > although no organization or individual has announced the attack, Iran believes that the attack was planned by Israel and accuses the United States of being behind the scenes. Is Iran retaliating? Is the conflict between Iran, Israel and the United States escalating? What is the impact of the incident on the US policy towards Iran in the future? On the 28th, Khamenei said in a statement that Iran’s top priority is to “clearly punish” the murderer and those who ordered the killing of Mukhsin fahrizad. On the same day, Rouhani also paid tribute to fahrizad, who was killed in the attack, and said that terrorist acts would not hinder Iranian scientists from continuing their efforts. < / P > < p > fahrizad is the head of Iran’s defense ministry’s nuclear program. Israeli Prime Minister Benjamin Netanyahu “named” fahrizad when talking about Iran’s nuclear program in 2018. Fahrizad is also a member of Iran’s Islamic Revolutionary Guard and is on the US sanctions list. Iran’s permanent representative to the United Nations, Majid taht rawashi, wrote to the Secretary General of the United Nations and the rotating president of the Security Council on the 27th, saying that there were “obvious signs of Israel’s responsibility” behind the assassination. He pointed out that in the past decade, several top Iranian scientists have been assassinated. < / P > < p > analysts pointed out that Iran vowed to avenge fahrizad, and if the retaliation resulted in the death of US personnel, the possibility of military conflict between the US and Iran will be significantly increased. However, Iran does not want to be involved in the war. < / P > < p > visiting scholar of Teheran University and Iran expert of Tsinghua University Liu Lanyu believes that the assassination of key figures in Iran by external forces is a kind of provocation or temptation, intended to stimulate Iran to make “excessive retaliation”, thus creating an excuse for military action against Iran. However, in the current sensitive period of power transfer in the United States, Iran may try to reduce the risk of triggering a direct conflict. < / P > < p > according to US media reports, the trump administration once considered attacking Iran in mid and early November, but gave up this plan after being dissuaded by the US military. < / P > < p > compared with the destruction of Iran’s nuclear program itself, analysts believe that the purpose of the assassination is to further undermine Iran’s nuclear agreement and squeeze the space for future diplomatic contacts between the new US government and Iran. < / P > < p > mark Fitzpatrick, a former U.S. State Department official in charge of nuclear non-proliferation affairs, said that Iran’s nuclear program has long gone beyond the stage of relying on individual scientists. The purpose of this assassination is not to destroy Iran’s “war potential”, but to destroy the diplomatic channels to deal with the Iranian nuclear issue. < / P > < p > the diplomatic team of US President elect Biden has made it clear that the new government will return to the track of the Iran nuclear agreement. Anthony brinkin and Jack Sullivan, the Secretary of state and Presidential Assistant for National Security Affairs announced by Biden not long ago, have participated in the negotiation of the Iran nuclear agreement and are firm supporters of the agreement. Sullivan previously said that returning to the Iran nuclear agreement will be a priority in the diplomatic field of the new US government. < / P > < p > Jeffrey Lewis, a professor at Middlebury Institute of International Studies in the United States, believes that the purpose of assassinating fahrizad is to “assassinate” the Iran nuclear agreement before Biden’s government takes office. < p > < p > Liu Lanyu believes that the Iran nuclear agreement belongs to Biden’s political performance as vice president in the Obama administration. Between January when Biden takes office next year and June when Iran holds the next presidential election, there may be a better negotiation window between the United States and Iran, but there are still many variables in their internal and external situations.