Kaja Kallas, the EU's foreign policy chief, said in an interview with the BBC that the idea of allowing Russia to keep temporarily conquered Ukrainian territories is"a trap that Putin wants us to fall into."

"The strongest security guarantee is a strong Ukrainian army," Kallas said, stressing the importance of establishing guarantees that are not"just on paper."

Bringing up the Alaska summit between Putin and Trump, the EU official stressed that the Kremlin leader had achieved"everything he wanted" and that this would have an impact on his interest in negotiating a peace agreement.

"He was received so warmly and wanted the sanctions not to be applied, which he got. Putin just laughs, he doesn't stop the killings, he intensifies them. We forget that Russia has not made any concessions," Kallas drew attention.

The Donbas region in eastern Ukraine has long been disputed by Russia, and this is also one of Moscow's demands as part of a peace agreement.

In response, Ukraine has consistently rejected both the cession of Donbas in exchange for peace and other territories occupied by the Russian military that Moscow wants to reclaim. Kiev has rejected all of these demands, considering them tantamount to surrender.