NATO Secretary-General Jens Stoltenberg has warned that NATO should not allow the situation in Ukraine to become a full-fledged war with Moscow.

Ruling out a no-fly zone on Friday, the chief expressed a responsibility to "prevent this conflict from escalating beyond Ukraine's borders to becoming a full-fledged war between Russia and NATO," adding in an interview with AFP that a no-fly zone over Ukraine would likely lead to a full war between Russia and NATO.

Last week, Kiev made an admission that establishing a no-fly zone over Ukraine as Russia's military operation in the country continues could potentially lead to a direct war between the Russian Federation and NATO, but it is still reiterating the plea for the action, Andriy Yermak, head of Volodymyr Zelensky's office said.

White House Spokesperson Jen Psaki said last Thursday that the United States is not interested in the establishment of a no-fly zone over Ukraine since it would require the military to shoot down Russian airplanes, which would lead to a war with Russia.

What is prominent about the Ukrainian talk of a Russia-NATO war is the fact that they came days after US President Joe Biden said, "You have two options: start a third World War, go to war with Russia physically. Or two, make sure that a country that acts so contrary to international law ends up paying the price."

Earlier today, US Defense Secretary Lloyd Austin underlined that establishing a no-fly zone over Ukraine could lead the United States into a direct war with Russia.

Frustration in Ukraine

The Secretary-General told Anadolu agency that he understands Kiev's "frustration" over the alliance's decision not to establish a no-fly zone over Ukraine.

NATO "understands frustration" in Ukraine, according to Stoltenberg, adding that "an escalation beyond Ukraine's borders would actually just cause even more suffering [and] more death."

Read more: Ukraine no longer to insist on joining NATO, may compromise Lugansk, Donetsk

"Implementing a no-fly zone in Ukraine would mean massive airstrikes against Russian air defense systems, leading to direct confrontation with Russia," Stoltenberg warned.

When asked about NATO's intentions regarding building up its potential, the NATO official said important decisions would be taken during the Madrid summit in June, calling on European allies to increase military budgets.

Regarding sanctions against Russia, Stoltenberg declared that all NATO allies are expected to sanction Russia and that Turkey was informed as well.