The National Iranian Oil Company signed Tuesday with Russian Gazprom a memorandum of understanding in the energy sector that includes Moscow investing $40 billion in developing the Kish gas field and the northern Fars oil field, increasing the production of the lower Fars gas field, and developing six Iranian oil fields.

The Iranian and Russian firms signed the biggest foreign investment deal in the Iranian economy, the Islamic Republic News Agency (IRNA) reported.

The Russians currently invest more than $4 billion in the Iranian oil industry, which is expected to see a ten-fold increase.

Russian President Vladimir Putin's spokesperson, Dmitry Peskov, revealed Monday that Russia handed Iran a draft agreement about comprehensive strategic joint cooperation between the two countries.

Putin is set to land in Iran today for talks with Iranian President Ebrahim Raisi and his Turkish counterpart Recep Tayyip Erdogan for a meeting on the Astana peace process.

Moscow, Tehran, and Ankara have been engaged in the Astana peace process for years now, a forum meant to bring to a close the war on Syria that has been raging on for more than 11 years.

Iranian-Russian relations and partnership have taken to new heights recently, especially in light of reciprocal visits, the signing of several agreements, and Tehran and Moscow seeing eye to eye on various issues.

Kremlin aide Yury Ushakov said Monday that "Iran is an important partner of Russia. Relations are of a friendly nature, have a long history, and are developing very effectively in the widest range of areas. Both sides have plans to bring bilateral cooperation to a new level - the level of strategic partnership. A new interstate agreement is being prepared."