Mikhail Kamynin's statement came after U.S. Ambassador in Ukraine William B. Taylor offered to help Ukraine on Wednesday, if it decided to review its gas deals with Russia.
Ukraine's prime minister-in-waiting Yulia Tymoshenko said Thursday that she would review all of Ukraine's gas deals, including those with Russia, and seek lower prices.
"Russia's gas relations with Ukraine are a bilateral matter," Kamynin said. "The agreements reached in 2006 signaled our joint choice for a new relations format, with due respect for the interests of Russia and Ukraine."
The spokesman also said the agreements signed in February 2006 to put an end to a bitter gas price dispute, were aimed at building energy security in Europe and the world.
The gas price row between the former Soviet neighbors in January led to Russia's Gazprom suspending supplies to Ukraine, which affected European countries. Gazprom then accused Ukraine of siphoning off Europe-bound gas, an allegation dismissed by Ukrainian authorities.
In late April, the U.S. Wall Street Journal reported that U.S. justice officials had opened an investigation into the sole supplier of Russian and Central Asian gas to Ukraine, Rosukrenergo, which they said was opaque.
Rosukrenergo is 50% owned by a subsidiary of Russian energy giant Gazprom, and the other 50% is held by Austria's Raiffeisen Investment.
