Ukraine needs more aircraft, helicopters and shoulder-launched missiles for a successful counter-offensive since Russia's dominance in the air is the second largest problem, Foreign Minister of Ukraine Dmytro Kuleba has said.

"The biggest problem on the counter-offensive is the sustainability of the supply of artillery ammunition, and in sufficient quantities. And the second largest problem of the counter-offensive is Russia's dominance in the air," he said in an interview with The Telegraph.

The minister stressed that "the biggest mountain that we have to climb is to ensure the sustainability of deliveries of artillery ammunition," and added that this is still the unconquered summit of "weapons diplomacy."

Kuleba also said that success on the battleground relates with the direction in which the diplomatic effort will go. In this regard, he said that this counter-offensive or the next counter-offensive should not be seen as the decisive or the final one.

"Of course we are cautious. We are aware of the fact that if the achievements on the ground will not be perceived as success, voices saying 'okay, we tried but it doesn't work militarily, so we have to put them at the table and negotiate' will become louder," the minister said.

He rejected the suggestion that calls from U.S. Republicans for an end to support for Ukraine represented the party's mainstream, however, and said he expected bi-partisan American support for Ukraine to be sustained.

Kuleba also said Ukraine is still trying to persuade the United States to supply ATACMS missiles for long-range precision strikes.