Binyamin Netanyahu, the Israeli prime minister, has urged Russia to support calls for new sanctions against Iran over its nuclear programme.
During talks in Moscow on Monday, Netanyahu asked Dmitry Medvedev, the Russian president, to back "sanctions with teeth" targeting Iran's energy sector, an Israeli official, speaking on condition of anonymity, said.
Iran's announcement last week that it had begun making higher-grade uranium has been met with calls for additional sanctions from the United States and it allies, who accused Tehran of seeking atomic weapons, a charge it denies.
Russian officials have in recent days indicated that Moscow could support a tougher stance on Iran, although neither Medvedev nor Vladimir Putin, the country's prime minister, have publicly commented on the situation for weeks.
Russia, which wields a veto in the United Nations Security Council, has been deeply disappointed by Tehran's refusal to send uranium abroad for enrichment in Russia, a deal Moscow hoped could allay Western fears.
Netanyahu told a cabinet meeting hours before he was due to leave for Russia for the two-day visit that a range of issues would be discussed but "first and foremost Iran".
"Israel believes that strong pressure must be applied to Iran, especially very tough sanctions," he said.
The Kremlin said in a statement ahead of the meeting that the Iran standoff would be discussed, adding that Russia was "working with international partners to unblock the situation through political means".
As well as Medvedev, Netanyahu is due to meet Jewish community leaders later on Monday and hold talks with Putin on Tuesday, officials said.
Russia has recently questioned the "sincerity" of Iran's pledges not to develop nuclear weapons and, in an apparent policy shift, said fresh UN sanctions on Tehran were a "realistic" option.
It has also yet to fulfil a contract to deliver sophisticated S-300 missile systems to Tehran, a deal that worried Israel as it would significantly strengthen Iranian air defences against military action.
Iran declared on Tuesday it had started the process of producing 20 per cent enriched uranium, as the United States stepped up its efforts to pass a new round of sanctions against Tehran by the UN Security Council.
Israel, considered to be the Middle East's sole, if undeclared, nuclear power, considers Iran its top enemy after aggresive statements against it by Mahmoud Ahmadinejad, the Iranian preident.
Russia has long-standing ties with Tehran and is helping to build Iran's first civilian nuclear power plant in the city of Bushehr.
This is Netanyahu's first official trip to Moscow since taking office a year ago, but follows a clandestine visit in September, a secretive move that highlighted the key role Russia plays in the nuclear standoff.