The Washington Post says top Ukrainian officials told the director of the US Central Intelligence Agency that they aim to retake substantial territory from Russia by autumn, and force Moscow into cease-fire talks by the end of this year.

US media on Friday quoted multiple sources as saying CIA Director William Burns met President Volodymyr Zelenskyy and top Ukrainian officials during his secret visit to Ukraine in June.

Burns' arrival reportedly preceded the aborted armed rebellion by the leader of the Wagner mercenary group.

During the visit, US media said military planners in Kyiv revealed the strategy behind the ongoing Ukrainian counteroffensive against Russia.

The report says that they want to move artillery and missiles near the border of Russian-controlled Crimea, push further into eastern Ukraine, and then start negotiations with Moscow.

The Washington Post reports that Ukraine is trying to hold hostage the peninsula, which is home to Russia's prized Black Sea Fleet. Russia unilaterally annexed Crimea in 2014.

Meanwhile, the Chairman of the US Joint Chiefs of Staff General Mark Milley said on Friday he was not surprised that progress was slower than predicted.

Speaking to an audience at the National Press Club in Washington, Milley said, "What I had said was this is going to take six, eight, 10 weeks, it's going to be very difficult. It's going to be very long, and it's going to be very, very bloody." He added, "And no one should have any illusions about any of that."