Prime Minister Binyamin Netanyahu lobbied Moscow on Monday for “very tough sanctions” to be imposed on Iran in order to convince the Islamic Republic to end its nuclear development program. The move came during a two-day visit to Russia that began late Sunday, in response to an announcement by Iranian President Mahmoud Ahmadinejad last Thursday that the Natanz nuclear facility had begun to enrich uranium up to 20 percent.

The stepped-up uranium enrichment program is part of continued Iranian defiance of a U.N. Security Council ban on its unsupervised nuclear development activities. Israel, the United States and other Western nations believe Iran is intent on using its nuclear technology to build an atomic weapon, possibly to annihilate the Jewish State.

“What is needed now are very tough sanctions that can influence this regime and severe sanctions that will considerably and convincingly harm the import and export of oil,” Netanyahu said.

Russian President Dmitry Medvedev expressed a willingness to listen to Israel's appeal, telling journalists at the start of his meeting with Netanyahu that Israel is no “ordinary partner” with Russia, but rather a country with whom there are long-term ties. He also referred to the population ties between the two nations, an apparent nod to Russian Jewry.

Following their talks, Netanyahu said he had told Medvedev about the need for “sanctions with teeth. They can bite only if they have teeth. Diluted sanctions don't work,” he said pointedly.

A spokeswoman from the Kremlin who accompanied Netanyahu at the news conference declined to comment on his remarks.

Until recently, Russia has had close ties with Tehran and has helped the Islamic Republic build its nuclear power station at Bushehr. Russia had also rejected Israel's request to freeze its sale to Iran of the advanced S-300 anti-missile air defense system that could be used to defend its nuclear facilities from attack.

However, Moscow recently was disappointed with Iran's rejection of an IAEA deal to send its uranium abroad – specifically to Russia – for enrichment, choosing instead to retain its ability to enhance the nuclear fuel at home.

That rejection may inspire Moscow, which has veto power in the U.N. Security Council, to support the United States in its bid to impose sanctions on the Islamic Republic.

In an apparent change of heart, Medvedev also reportedly told Netanyahu on Monday that he would delay the sale of the S-300 system to Iran. However, he did not say the sale would be canceled. A senior governement minister said hours before Netanyahu's arrival that the sale of the missiles would continue.