MOSCOW >> Saudi King Salman arrived in Moscow today on the first ever visit by a Saudi monarch to Russia.

As part of the four-day trip, the king is due to meet with Russian President Vladimir Putin on Thursday for talks in the Kremlin expected to focus on the global oil market and the conflict in Syria.

Ties between the two countries were often strained in the past. During Cold War times, the Saudis helped arm Afghan rebels fighting against the Soviet invasion.

More recently, tensions were high over the war in Syria, in which Russia has staunchly backed Syrian President Bashar Assad while Saudi Arabia has supported his foes.

However, relations have begun to improve in recent years and King Salman’s heir, Crown Prince Mohammed bin Salman, has held several meetings with Putin.

A thaw between Moscow and Riyadh helped reach November’s deal in which OPEC and 10 other oil-producing countries, including Russia, agreed to cut their production in a bid to combat a supply glut and shore up crude prices.

The king has brought a massive delegation of Saudi businessmen with him, and the two parties are expected to negotiate new investment deals, including in the energy sector. The Saudis also have been eyeing Russian nuclear power technologies and appear ready to expand food imports from Russia, which is set to remain the world’s biggest wheat exporter this year.

While Riyadh has maintained its strategic alliance with the U.S., it has also sought to improve ties with Russia in a bid to counter the influence of its arch-rival, Iran and dissuade the Kremlin from too close a partnership with Tehran.

Asked about ties with Riyadh during a panel discussion at an international energy conference today, Putin responded that Moscow doesn’t see close U.S.-Saudi relations as an obstacle for closer cooperation with the Saudis, and added that alliances tend to shift.

“Is there anything in the world that stays unchanged?” Putin said. “I think that all things change.”