Jake Sullivan, the U.S. President's national security adviser, said that Russian President Vladimir Putin's recent conscription of reservists into the army and referendums held in the occupied regions of Ukraine will not be an obstacle to further U.S. assistance to Ukraine.

"What Putin has done is not exactly a sign of strength or confidence, frankly, it's a sign that they're struggling badly on the Russian side … And we're going to help the Ukrainians be able to take advantage of the gains they've made, and to continue to push back against the Russian forces that are brutally occupying portions of their country," Sullivan said in an interview with Face the Nation on the CBS TV channel on Sunday.

He noted the "low morale" of Russian soldiers, that the Russian Federation is "disorganized and losing territory, to a capable Ukrainian force," and there is "a huge amount of infighting among the Russian military leadership." At the same time, Sullivan noted that the Russian Federation "remains a dangerous foe and is capable of great brutality," as evidenced by the mass graves found in Izium of Kharkiv region.

The adviser to the U.S. president promised that Ukraine would receive more artillery, air defense systems and tanks, noted that the USA provided Ukraine with weapons worth more than $15 billion and facilitated the transfer of tanks to Ukraine by NATO allies.

"We continue to see our obligation being providing Ukraine all that it needs to be able to effectively defend itself and defend its country and defend its freedom," Sullivan said.