Two U.S. officials who spoke on the condition of anonymity said the arrangement would be similar to the NATO mutual defense agreement. But crucial details remain unsettled as negotiators seek a deal that Russia will approve.

The proposal of so-called Article 5-like guarantees comes amid marathon talks among special envoy Steve Witkoff, President Donald Trump’s son-in-law and adviser Jared Kushner and Ukrainian and European officials in Berlin as Washington tries to pressure Kyiv into accepting terms that will end the war.

A 1,000-strong "dark fleet" of rogue tankers evading sanctions has become a new target for the U.S. and Ukraine, according to a senior maritime intelligence analyst.

BERLIN, Dec 15 (Reuters) - European leaders said they had agreed on Monday any decisions on potential Ukrainian territorial concessions to Russia could only be made once robust security guarantees were in place which should include a European-led multinational force.

Ukraine has relinquished its ambition of joining the NATO military alliance in exchange for Western security guarantees as a compromise to end the war with Russia, President Volodymyr Zelenskyy said ahead of talks with U.S. envoys in Berlin.

Russian Deputy Foreign Minister Sergey Ryabkov told ABC News during an exclusive interview in Moscow on Monday that he believes the warring parties are close to a deal.

U.S. peace negotiators have told Ukraine during peace talks in Berlin that it must agree to withdraw its forces from the eastern Donetsk region as part of any deal to end the nearly four-year-old war,