KYIV, Ukraine (AP) — U.S. President Donald Trump’s special envoy Keith Kellogg said in Kyiv on Monday that officials are “working very, very hard” on efforts to end the three-year war between Russia and Ukraine, as a lack of progress fuels doubts about whether a peace settlement could be on the horizon.

Ukraine launched a large drone strike Sunday that caused damage at Russia's Kursk Nuclear Power Plant and a major fuel export terminal hundreds of miles away.

President Donald Trump said on Monday that he has not discussed specific security guarantees for Ukraine and reaffirmed the U.S. commitment to support the country.

Secretary of State Marco Rubio told European counterparts Thursday the US will participate in post-war security guarantees for Ukraine but that the Trump administration believes Europe should take the lead,

Security guarantees for Ukraine have emerged as a key topic of negotiation as US President Donald Trump seeks to broker a peace deal to end Russia’s war.