Talks in Russia between President Vladimir Putin and Israeli PM Benjamin Netanyahu in Russia are to focus on the conflict in Syria, official say.
Russia is concerned by Israeli air strikes on targets inside Syria, while Israel is unhappy at shipments of Russian weapons to Damascus.
Moscow has been at the centre of recent diplomatic efforts to end the conflict.
Meanwhile, a video has emerged that appears to show a Syrian rebel cutting out and eating the heart of a soldier.
"I swear to God we will eat your hearts and your lives, you soldiers of Bashar the dog," the man says as he bends over a body and cuts out the heart with a knife.
He then stands up and proceeds to place the organ in his mouth.
The authenticity of the footage, posted online on Sunday, cannot be authenticated, but Peter Bouckaert of Human Rights Watch identified the man as Abu Sakkar, a well-known rebel from the city of Homs and founder of the Farouq Brigade of the Free Syrian Army.
"The mutilation of the bodies of enemies is a war crime. But the even more serious issue is the very rapid descent into sectarian rhetoric and violence," Mr Bouckaert told Reuters news agency.
The UN says 70,000 people have been killed since the uprising against President Bashar al-Assad began in March 2011. The UK-based Syrian Observatory for Human Rights puts the death toll at more than 80,000.
The bloodshed will be the focus of discussions between Mr Netanyahu and Mr Putin on Tuesday.
The location of their meeting has not been announced officially, although it is widely thought to be the Russian Black Sea resort of Sochi.
"During the meeting an exchange of opinion is planned on key aspects of bilateral ties," the Kremlin said in a statement on Monday. "It is expected that major attention will be paid to the current situation in the Middle East, first and foremost in Syria."
Mr Netanyahu is expected to request that Russia to stop supplying the Syrian military with advanced weapons systems. Recent deliveries have included air defence missiles and artillery systems.
Last week, Russian Foreign Minister Sergei Lavrov said Moscow was not violating any international sanctions and would honour already signed contracts, but avoided confirming reports that it was preparing to sell Damascus S-300 air defence batteries.
The BBC's Steve Rosenberg in Moscow says the S-300 fires long range surface-to-air missiles that could pose a challenge to any possible aerial campaign in Syria.
Earlier this month, the Syrian government accused Israel of bombing military facilities near Damascus. Israel declined to comment, but security sources said the air strikes had been aimed at preventing the transfer of Iranian-made missiles to Hezbollah in Lebanon.
Following the attacks, the Russian foreign ministry warned that the "further whipping-up of armed confrontation" sharply increased the risk of "pockets of tension" in Syria and Lebanon.
In recent days, Russia has been at the centre of diplomatic efforts to end the conflict, our correspondent says.
President Putin has had talks on Syria with UK Prime Minister David Cameron and the US Secretary of State, John Kerry. Mr Kerry and Mr Lavrov have also agreed to work towards convening a new international conference to find a political solution.
It will try to convince both the Syrian government and opposition to accept a solution based on the core elements of the final communique issued on 30 June 2012, after the UN-backed Action Group for Syria meeting.
The communique called for an immediate cessation of violence and the establishment of a transitional government that could include officials serving under President Assad and members of the opposition.
On Monday, Prime Minister Cameron and US President Barack Obama expressed hope that Russia would help persuade President Assad to step down.
"As a leader on the world stage, Russia has an interest, as well as an obligation," Mr Obama told reporters in Washington, though he admitted that there remained "lingering suspicions" about Moscow's commitment to ending Mr Assad's rule.
Mr Obama also sounded a note of caution about the new conference, which US officials said was likely to be held in early June and not at the end of May as hoped.
"I'm not promising that it's going to be successful," he said, adding that "once the furies have been unleashed", it is "very hard to put things back together".
Mr Cameron said the UK would call for greater flexibility in the EU arms embargo on Syria, and that it would double non-lethal aid to the rebels, shipping armoured vehicles, body armour and generators.