Sochi: Israeli Prime Minister Benjamin Netanyahu has told Russian President Vladimir Putin that Israel was prepared to act unilaterally to prevent an expanded Iranian military presence in Syria.

Israel fears an eventual Assad regime victory could leave Iran with a permanent garrison in Syria, extending a threat posed by the Iranian-backed Hezbollah in Lebanon to its north.

Russia intervened in the civil war on behalf of Syrian President Bashar al-Assad in 2015, joining a de facto alliance with Iranian forces, Lebanese Hezbollah and other Shiite Muslim militias helping Damascus beat back Islamic State and other Sunni Muslim insurgent groups.

Meeting Mr Putin in the Black Sea resort of Sochi, Mr Netanyahu said Iran was fighting to cement an arc of influence from the Gulf to the Mediterranean.

"Iran is already well on its way to controlling Iraq, Yemen and to a large extent is already in practice in control of Lebanon," Mr Netanyahu told Mr Putin.

"We cannot forget for a single minute that Iran threatens every day to annihilate Israel," he said. "Israel opposes Iran's continued entrenchment in Syria. We will be sure to defend ourselves with all means against this and any threat."

Mr Putin, in the part of the meeting to which reporters had access, did not address Mr Netanyahu's remarks about Iran nor his threat to take unilateral military action.

But at the United Nations, Russian UN Ambassador Vassily Nebenzia told reporters the de-escalation zones established in Syria, of which Iran is guarantor alongside Turkey and Russia, are "real progress on the way to end that tragic war".

"We know the position of Israel towards Iran but we think that Iran in Syria is playing a very constructive role," Mr Nebenzia said.

In parallel to lobbying Moscow, Israel has been trying to persuade Washington that Iran and its guerrilla partners, not Islamic State, pose the greater common threat in the region.

"Bringing Shiites into the Sunni sphere will surely have many serious implications both in regard to refugees and to new terrorist acts," Mr Netanyahu told Israeli reporters after the three-hour meeting - his sixth with Putin since September 2015.

"We want to prevent a war and that's why it's better to raise the alarm early in order to stop deterioration."

After the meeting, Mr Netanyahu was due to fly back to Israel for talks with US peace envoys Jared Kushner - US President Donald Trump's son-in-law, Jason Greenblatt and Dina Powell, who are on a Middle East tour.

Russia has so far shown forbearance toward Israel, setting up a military hotline to prevent their warplanes or anti-aircraft units clashing accidentally over Syria. Israel's air force said last week it had struck suspected Hezbollah arms shipments around 100 times in Syria during the civil war, rarely drawing retaliation and apparently without Russian interference.

Russian diplomats have argued that Moscow's stake in Syria deters Iran or Hezbollah from opening a new front with Israel.

"We take the Israeli interests in Syria into account," Alexander Petrovich Shein, Russia's ambassador to Israel, told its Channel One television. "Were it up to Russia, the foreign forces would not stay."

Zeev Elkin, an Israeli cabinet minister who joined Mr Netanyahu in Sochi, said in a radio interview after the talks that he had "no doubt that [the meeting] will lead to practical steps".

Reuters