Russian President Vladimir Putin is due to meet German Chancellor Angela Merkel in the Black Sea resort of Sochi on Friday, as Moscow and Europe make rare joint efforts to save the Iran nuclear deal.
The pair's first face-to-face meeting in a year will take place less than a week before French President Emmanuel Macron is due to visit Russia.
The meeting will take place in Putin's Sochi residence and is expected to be dominated by US President Donald Trump's decision to pull out from the Iran agreement.
The fallout over the Iran deal is a rare topic for rapprochement between Europe and Moscow, whose relations are marred by disagreements over the Syria conflict, Moscow's 2014 annexation of Crimea and the subsequent war in eastern Ukraine.
These tensions have only worsened in recent months following the poisoning of former Russian spy Sergei Skripal in Britain that led to an unprecedented wave of expulsions of Russian diplomats from Western countries.
As part of the historic 2015 Iran deal, Tehran agreed to curb its nuclear program by pledging not to seek an atomic bomb in exchange for the lifting of some international sanctions on the Middle East country.
The Europeans now want to avoid at all costs Tehran abandoning the deal and relaunching its program to acquire a nuclear weapon.
They also want to protect their economic interests in Iran, threatened by Washington's reintroduction of sanctions.
The Kremlin, allied with Iran in its support for the Bashar al-Assad regime in the Syrian conflict, has in recent days increased its diplomatic efforts to try to maintain the agreement it described as "crucial for regional stability and for the stability of the entire world".
Iran's foreign minister Mohammad Javad Zarif was in Moscow Monday before visiting Brussels for talks Iran said were aimed to "seek assurances" from countries that signed the deal.
Merkel's visit comes ahead of Macron's trip to Saint Petersburg on May 24.
Putin and Merkel last met for bilateral talks in May 2017, also in Sochi.
"It will be a very interesting exchange of views, since there has been no direct contact (between the two leaders) for a very long time," said Kremlin advisor Yury Ushakov.
Putin, who worked as a KGB agent in Dresden in the late 1980s, and Merkel, who grew up in East Germany, speak each other's languages.
- Syria, Ukraine and energy -
The pair are also expected to discuss the Syrian crisis and the conflict between Kiev and eastern Ukraine's pro-Russia rebels.
Berlin and Moscow, along with Paris, signed peace agreements in Minsk in 2015 that aimed to put an end to a conflict that has left more than 10,000 dead since it began in April 2014.
On May 12, Merkel expressed concern about the situation in Ukraine, where she said there are "violations of the truce every night and loss of life every day".
According to Moscow, the two leaders will try to organise a four-way meeting with the presidents of France and Ukraine to advance a possible UN peacekeeping meeting. The last summit between the four countries in October 2016 was inconclusive.
Merkel and Putin are also expected to discuss the construction of a second North Stream underwater pipeline linking the two countries via the Baltic Sea, a project several EU countries oppose.
North Stream 2 aims to double the capacity of North Stream 1 by the end of 2019, and allow more Russian gas to arrive directly to Germany via the Baltic Sea, bypassing Ukraine.
German Chancellor Angela Merkel's meeting with President Vladimir Putin in Sochi is expected to be dominated by the Iran deal