Sergei Naryshkin, who heads up Russia's SVR Foreign Intelligence Service and is a close ally of President Vladimir Putin, accused Nato of upping the ante in the conflict by supplying Kyiv with more advanced weapons.
"Nato is raising the stakes because they still have dreams of a strategic defeat over Russia," Naryshkin said in a televised interview with the state-run Ria news agency released on Wednesday.
"But this will not happen." His comments come as the United States is readying its latest package of military aid for Ukraine, worth some $2 billion. Supplies are expected to include rockets with a range of up to 150 kilometers (94 miles) for the first time.
Washington has previously been hesitant to supply Kyiv with such long-range weapons, apparently fearing they could be used in attacks on Russia itself, which could bring Moscow and Nato closer to the brink of direct conflict.
Naryshkin criticized Washington's latest promises of military aid, saying Moscow had "taken note of the expansion in both the volume and the range of military equipment being supplied."
He said the United States and its allies were "determined to wage war with Russia to the last Ukrainian."
Following promises by the United States, Germany and several other European countries to deliver dozens of tanks to Ukraine, Russian officials such as Foreign Minister Sergei Lavrov and Kremlin spokesman Dmitry Peskov have accused Nato countries of taking a more active role in the war.
Kyiv and the West say military supplies are vital to help Ukraine defend itself against what they say is an illegal war of aggression being waged by Russia which sent tens of thousands of troops into Ukraine in February last year in what it called a "special military operation."
Reuters