Ukraine President Volodymyr Zelenskyy on Friday said that his country will formally apply for a fast-track membership of the North Atlantic Treaty Organisation.

His announcement came close on heels of Russian President Vladimir Putin declaring the annexation of four territories in Ukraine, AFP reported. He also urged Kyiv to lay down its arms and negotiate an end to the fighting that has been going on since February.

Zelenskyy said on Friday that NATO member countries and Ukraine are already de facto allies.

“We trust each other, we help each other and we protect each other,” he said in an address to the nation. “This is what the alliance is. De facto. Today, Ukraine is applying to make it de jure [as per law].”

The Ukrainian president also said that his country was ready for a dialogue with Russia, but not with Putin.

“It was our state that always offered Russia to reach an agreement on coexistence on equal, honest, decent and fair terms,” he said. “It is obvious that this is impossible with this Russian president. He does not know what dignity and honesty are. Therefore, we are ready for a dialogue with Russia, but...with another president of Russia.”

Earlier on Friday, Putin announced at a ceremony that the residents of territories of Luhansk, Donetsk, Kherson and Zaporizhzhia “are becoming our citizens forever”, AFP reported.

Putin warned that he could use nuclear to retain control over the four territories. “We call on the Kyiv regime to immediately stop fighting and stop all hostilities... and return to the negotiating table,” he said.

The European Union described the annexations as being illegal, the Associated Press reported. It said that it would never recognise the “illegal referendums” that Russia held ““as a pretext for this further violation of Ukraine’s independence, sovereignty and territorial integrity”.

Russia launched an invasion of Ukraine on February 24. The Kremlin described its actions as a “special operation” to demilitarise and “de-Nazify” Ukraine. However, Kyiv and several Western nations have said that this is a baseless pretext for a war of choice by Putin.