Spokespersons for Cargill and Viterra's Russian operations said that their respective companies do not plan to leave the country. Uralchem declined to comment.

Dozens of foreign firms, including McDonald's, have left Russia since Moscow sent thousands of troops to Ukraine on Feb. 24. However, food supplies are not targeted by Western sanctions, and Viterra and Cargill continue operating in Russia.

In a letter sent by Uralchem Chief Executive Dmitry Konyaev to President Vladimir Putin on Nov. 21, the company asked the president to support its proposal, saying that Viterra and Cargill's grain trade overlaps with Uralchem's business.

On Nov. 22 Putin signed "agree" on the letter and instructed Prime Minister Mikhail Mishustin to consider the proposal.

The existence of the letter was first reported by Russia's Kommersant newspaper on Thursday.

Russia is the world's largest wheat exporter and a major supplier of fertilisers to global markets.

Uralchem wants to become a grain trader because many Russian farmers who sell grain overseas via foreign commodities houses such as Viterra and Cargill purchase fertilisers from Uralchem, a source at the company told Reuters.

"The assets of these companies offer good synergy effect. But so far we are only talking about negotiations, which could be initiated if Viterra and Cargill are interested," the source said.

Without their consent to leave, "no one would be twisting their arms," the source added.

Viterra is part-owned by Switzerland-based mining and trading giant Glencore.

It is not the first attempt to draw Putin's attention to global commodities traders in Russia. In September, sanctions-hit Russian VTB Bank in a letter to Putin called for the activities of Western grain traders in Russia to be curbed.

However, agriculture minister Dmitry Patrushev said in early December that Russia does not intend to "kick out" foreign grain traders.

Cargill owns a stake in the grain terminal in the Black sea port of Novorossiisk. Viterra and VTB share ownership of a grain terminal in the Black Sea port of Taman.

Uralchem is building an ammonia export terminal in Taman, which it plans to launch late next year.

(Reporting by Polina Devitt; additional reporting by Gus Trompiz; editing by Susan Fenton)

By Polina Devitt