“If they continue to get no support from the US, in a month or two, it is very likely that the Russians will achieve more territorial gains and have more success against Ukrainian frontlines in terms of just territory gain,” Kirby told reporters.
He pointed out that such a situation could happen in eastern Ukraine, but also potentially in the south of the country.
Kirby stressed that the situation on the ground is dire.
US President Joe Biden said on Tuesday that the need to provide additional support to Ukraine is urgent.
Russia has repeatedly warned NATO countries that arms supplies to Ukraine would be considered legitimate targets. Moscow has accused NATO countries of "playing with fire" by arming Ukraine, emphasizing that such actions hinder the possibility of Russia-Ukraine negotiations.