The top diplomat of the European Union (EU) has warned against pushing Ukraine to give up territories to Russia as part of a future peace deal.

Speaking in her first UK interview since EU leaders joined Donald Trump's White House peace talks with Ukraine, Kaja Kallas told the BBC's Today programme that letting Russia keep Ukrainian territories was a "trap that Putin wants us to walk into".

The Donbas region in eastern Ukraine has long been contested by Russia, with military aggression forcing 1.5 million Ukrainians to flee over the past decade.

Ukraine has consistently rejected conceding Donbas to the Kremlin in exchange for peace, though Trump stressed the need for "swapping of territories".

Kallas - who has been placed on the Kremlin's "wanted list" - also spoke at length about "credible and robust" security guarantees for Ukraine.

She admitted that there were not many "concrete steps" for a deterring force at this stage in negotiations.

"The strongest security guarantee is a strong Ukraine army," she said, outlining the importance of establishing guarantees that were "not just on paper".

She said it was up to member states of the "coalition of the willing" to determine exactly what they could contribute, and that it was not yet clear in what capacity those forces would operate.

Leaders from key EU countries, including France, Germany, Italy and Finland, joined Ukrainian President Volodymyr Zelensky for talks at the White House last week, days after Trump hosted Russian President Vladimir Putin in a military base in Alaska.

On the Alaska summit, Kallas said that Putin got "everything he wanted" and that would impact his interest in negotiating a peace deal.

"He got such a welcoming and he wanted sanctions not to be put in place, which he also achieved.

"Putin is just laughing, not stopping the killing but increasing the killing," Kallas said. "We are forgetting that Russia has not made one single concession."

She added that the EU had put together the 19th package of sanctions to pressure the Russian leader into further discussions.

Meanwhile, Trump on Thursday set a two-week time frame for evaluating peace talks between Russia and Ukraine.