KIEV, Aug. 10 - Prime Minister Mykola Azarov on Wednesday warned Russia that a failure to renegotiate the 10-year natural gas agreement signed in January 2009 would “very seriously undermine” long-term relations between the two countries.

The warning is the most serious yet in the 15 months that Ukraine has been trying - unsuccessfully - to renegotiate the agreement towards lowering Russian gas prices.

“Is it in Russia’s interests? Is any unequal agreement in the interest of long-term cooperation?” Azarov said speaking at a Russian-Ukrainian economic forum in Kiev.