The commander of Ukraine’s ground forces, in an interview published Friday, said he expected the 26-month-old war against Russia to enter a critical phase in the next two months as Moscow tries to exploit delays in supplying weapons to Kyiv.

“Russia knows that if we receive enough weapons within a month or two, the situation could turn against them,” General Oleskander Pavliuk told The Economist magazine.

Supplies of U.S. weapons slowed for months while an aid package proposed by President Joe Biden was held up by wrangling in Congress. The measure was passed late last month.

President Volodymyr Zelenskyy said on Friday that Ukraine still needed “timely” future supplies of key weapons.

Pavliuk’s interview preceded Friday’s Russian armored attack into areas of northeastern Kharkiv region.

The Economist said Pavliuk believed Moscow would stay focused on its slow advance through Luhansk and Donetsk regions in the east. Ukraine needed more air defense, he said, and would get a boost with the anticipated delivery of F-16 fighter jets.

Russia, Pavliuk told the magazine, “is testing the stability of our lines before choosing the most suitable direction.”

Russian forces have taken a string of villages in the east after capturing the town of Avdiivka in February.

Pavliuk appeared to play down the significance of possibly losing the eastern town of Chasiv Yar, described as a gateway to other cities that Moscow is targeting, like Kramatorsk and Sloviansk.

The loss of Chasiv Yar, he said, would have no “decisive significance” as it was just “a regular urban settlement.”

Pavliuk also said he believed there should be a renewed focus on Kyiv, from where Russian forces pulled back early in the invasion after initially trying to advance on the capital city.

“Defending Kyiv remains one of our main concerns, no matter how tough it is in the east,” he told The Economist. “It is the heart of Ukraine, and we know the key role defense of the capital will play in the future.”