REUTERS CEO of National Joint-Stock Company Naftogaz of Ukraine Andriy Kobolyev says natural gas stocks in Ukraine&#39;s underground storage facilities (USFs) have exceeded 20 billion cubic meters (bcm), which means full implementation of the plan, allowing Ukraine to pass the heating season even if Russia terminates the transit contract from January 2020. "Today we can already say we have managed to fully implement ourplans for preparing for a difficult winter. I&#39;d like to thank everyone who helped find financial resources to this end, who ensured the purchase of gas and its injection into underground storage facilities," he wrote on Facebook. According to Kobolyev, gas reserves in Ukrainian USFs expanded beyond 20 bcm, which is over 4 bcm more than the last year&#39;s figure and is the highest level over the past nine years. Read alsoGazprom&#39;s debt before Naftogaz grows to over US$2.8 bln since Feb 2018 "There is enough gas in the USFs to ensure reliable operation of the gas transmission system and gas supply to all Ukrainian consumers this winter even if Russia resorts to halt transit via Ukraine," he said. As UNIAN reported earlier, Ukraine on April 5 started the season of pumping natural gas into its underground storage facilities. It is planned to accumulate more than 20 bсm in the USFs before the start of the heating season in the middle of October. By the start of the 2018-2019 heating season, Ukraine had accumulated 17.2 bcm of gas in its underground storage facilities, which was a record high natural gas stock over the past six years. Additional volumes of gas in storage facilities are required to smoothly pass the heating season if Russia completely halts the transit of gas via the territory of Ukraine. Read alsoGas transit talks: Ukraine seizing initiative or taking Russian bait? The existing gas transit contract between Ukraine and Russia&#39;s Gazprom was signed in 2009 for a period of 10 years. Once it expires (from 2020), the Russian monopoly plans to minimize gas transit via the Ukrainian territory.