MOSCOW (Reuters) - Israel promised Russia it would not launch an attack on Iran, Russian President Dmitry Medvedev said in an interview aired on Sunday in which he described such an assault as “the worst thing that can be imagined.”

Russian President Dmitry Medvedev gestures as he speaks with members of the Valdai discussion group in GUM department store in Moscow September 15, 2009. REUTERS/Ria Novosti/Kremlin/Dmitry Astakhov

Israel has hinted it could forcibly deny Iran the means to make an atomic bomb if it refuses to suspend uranium enrichment and has criticized Russia for agreeing to supply to Tehran S-300 anti-aircraft weapons that could complicate an attack.

In an interview with CNN recorded on Tuesday, Medvedev denied Moscow was backing Iran but said it had the right to supply defensive weapons and said sanctions against Tehran should only be used as a last resort.

An attack would lead to “a humanitarian disaster, a vast number of refugees, Iran’s wish to take revenge and not only upon Israel, to be honest, but upon other countries as well,” Medvedev said, according to a Kremlin transcript.

“But my Israeli colleagues told me that they were not planning to act in this way and I trust them.”

During a meeting in the Russian resort of Sochi in August, Israeli President Shimon Peres said Israel would not attack Iran, Medvedev said. After the meeting, Peres told journalists Medvedev had promised to reconsider a contract to sell S-300s to Iran.

“When he visited me in Sochi, Israeli President Peres said something important for us all: ‘Israel does not plan to launch any strikes on Iran, we are a peaceful country and we will not do this’,” Medvedev said.

Asked about the possible delivery of S-300s, Medvedev said Russia had the right to sell defensive weapons to Iran.

SANCTIONS

“Our task is not to strengthen Iran and weaken Israel or vice versa but our task is to ensure a normal, calm situation in the Middle East,” Medvedev said.

On Western calls for sanctions on Iran, he said such moves were often ineffective and action should only be taken as a last resort.

“Before speaking of applying additional sanctions, we should make full use of the existing possibilities,” he said. “We should be absolutely confident that we have no other option.”

Analysts have been watching for Russian concessions on Iran after the White House on Thursday canceled plans to site elements of a missile shield in Poland and the Czech Republic, but CNN interviewed Medvedev before the announcement.

Medvedev said he was hopeful Moscow’s relations with Washington would improve under President Barack Obama and described the chances of an agreement on a new treaty to reduce strategic nuclear weapons by year-end as “quite high.”

But he was critical of mixed messages coming from the White House.

Shortly after Obama hailed a “reset” of ties during a visit to Moscow in July, U.S. Vice President Joe Biden said Russia’s shrinking population base and “withering economy” would push it to make deals on nuclear arms reductions.

“This is simply an incorrect move,” Medvedev said. “Because while having only started to develop relations... with the Russian Federation, at the same time to strain them in such a way is to make a mistake.”