Vladimir Putin told Donald Trump he "will not back down" from Russia's goals in Ukraine during a phone call today, the Kremlin has said.
The Russian president spoke to his US counterpart for almost an hour, and Mr Trump "again raised the issue of an early end to military action" in Ukraine, Kremlin aide Yuri Ushakov told reporters.
In response, Mr Putin said "Russia will not back down" from its aims there, which include "the elimination of the well-known root causes that led to the current state of affairs," Mr Ushakov said.
The phrase "root causes" is shorthand for Moscow's argument that it was compelled to invade Ukraine in order to prevent the country from joining NATO.
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Ukraine and its European allies say this is a pretext to justify what they call an imperial-style war, but Mr Trump has previously shown sympathy with Russia.
At the same time, Mr Putin told the US president that Russia is ready to continue negotiating, the aide said.
The Russian president said any prospective peace deal must see Ukraine give up its NATO bid and recognise his country's territorial gains.
He also briefed Mr Trump on agreements made last month, which saw Russia and Ukraine exchange prisoners of war and dead soldiers.
Specific dates for the third round of peace talks in Istanbul were not discussed - nor was the US decision to halt some shipments of critical weapons to Ukraine.
Mr Putin and Mr Trump's call came after the Pentagon confirmed some weapons due to be sent to Ukraine have been held as it reviews military stockpiles.
The paused shipments include air defence missiles and precision-guided artillery, two people familiar with the situation have said.
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The decision led to Ukraine calling in the acting US envoy to Kyiv on Wednesday to underline the importance of military aid from Washington.
Kyiv also cautioned that the move would weaken Ukraine's ability to defend itself against intensifying Russian airstrikes and battlefield advances.
Mr Putin and Mr Trump's phone call was the sixth they have publicly disclosed since the US president returned to the White House in January.