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.

Oil prices climbed around 2% on Monday, continuing last week's gains, as traders anticipated more U.S. sanctions on Russian oil and Ukrainian attacks on Russian energy infrastructure that could disrupt supplies.

US President Donald Trump on Monday warned of "great consequences" if Russian President Vladimir Putin and Ukrainian President Volodymyr Zelenskyy fail to hold talks, while asserting that the ongoing war would not have occurred under his leadership.