The new chief of Britain’s foreign intelligence service MI6 accused Russian President Vladimir Putin of deliberately prolonging negotiations to put an end to the war in Ukraine, in an assessment that complicates Trump’s efforts to broker a deal by year-end.

The U.S. has agreed to provide unspecified security guarantees to Ukraine as part of a peace deal to end Russia's nearly four-year war, and more talks are likely this weekend, U.S. officials said Monday following the latest discussions with Ukrainian President Volodymyr Zelenskyy in Berlin.