NATO is a military alliance of 30 countries which functions on the principle of collective defence. It means that an attack on one NATO country means an attack on all NATO countries.

Russian President Vladimir Putin on Friday announced that Russia is annexing the four regions of Luhanks, Donetsk, Zaporizhzhia, and Kherson. Russia controls Luhansk and Kherson regions, about 60 per cent of the Donetsk region, and a large chunk of the Zaporizhzhia.?

Following this, Zelenskyy said, "We are taking our decisive step by signing Ukraine's application for accelerated accession to NATO."

It wasn't immediately clear what an "accelerated" application would mean as ascension to NATO requires the unanimous support of the alliance's members.

Zelenskyy said, "De facto, we have already proven compatibility with alliance standards. They are real for Ukraine — real on the battlefield and in all aspects of our interaction. We trust each other, we help each other, and we protect each other. This is the alliance."

Zelenskyy also repeated his pledge to reunite all of the Ukrainian territory now held by Russia.

He said, "The entire territory of our country will be liberated from this enemy — the enemy not only of Ukraine, but also of life itself, humanity, law and truth. Russia already knows this. It feels our power. It sees that it is here, in Ukraine, that we prove the strength of our values."

Responding to Putin's call for negotiations, Zelenskyy added, "We are ready for a dialogue with Russia, but with another president of Russia."

Ukraine's membership of NATO has been a red line for Ukraine and its and prospects of joining NATO was one of the justifications of launching the invasion on February 24, dubbed as a special military operation.?

The war has rapidly accelerated Ukraine's shift toward the West. During Russia's seven-month war, the country has shifted off Soviet-era weapon systems and used NATO-standard ordinance and weapons, though the process is still ongoing.

In June, the European Union (EU) agreed to put Ukraine on the path toward EU membership. That swiftness of that move —nearly unthinkable only months earlier— required unanimous approval among the bloc's often fractious members.

While there is considerable overlap among the members of the EU and NATO, securing agreement to allow Ukraine into the security alliance and its guarantee of mutual defense could be considerably more difficult.?

One immediate impediment to Ukraine joining is that it is already engaged in an active military conflict on its soil. The collective defence principle would mean that, in case Ukraine joins NATO, the entire alliance would be at war with NATO, whereas the NATO as well as the United States —at the forefront of helping Ukrainian war efforts with arms and intelligence— have stated policy of not deploying their personnel in combat with Russia.

(With AP inputs)