National joint-stock company Naftogaz Ukrainy has sent a letter with proposals to revise a contract on the volumes and conditions of natural gas transit via the country's territory from 2090 to 2019 to Russia's OJSC Gazprom, Board Chairman of Naftogaz Ukrainy Andriy Kobolev has said.

"This week we've sent a letter to OJSC Gazprom with a demand to change the transit contract. The process has been started," he said on the ICTV TV channel late on Monday.

He did not specify all the proposals of Ukraine regarding the revision of the contract.

"One of the elements for changing the transit contract is the amendments to the methods of gas metering – where it will be metered and how it will be controlled," he added.

As reported, Naftogaz Ukrainy several times criticized the transit contract for the absence of guarantees of the volumes of transit gas and the 'take and pay' conditions. In addition, Ukraine has raised the issue of revising the transit rate, believing the rate has been set too low.

Recently Kyiv raised the issue of revising the transit rate, believing that it was set too low. Ukraine also proposed to transfer the place of accepting Russian natural gas by European consumers to the Russian-Ukrainian border.

Earlier Kobolev said that the company will continue achieving its revision via negotiations, but if the talks are a failure, the company will file a claim at the Stockholm arbitration institution.

Kobolev said that along with transit rates, there are several other serious problems with the contract. For example, the contract does not allow Naftogaz Ukrainy to clearly forecast the transit volume for upcoming periods.

Naftogaz Ukrainy unites oil and gas production assets in Ukraine, and is the country's gas transit, underground gas storage, and oil pipeline transportation monopoly.