Russia said Tuesday its military will sharply cut back operations near Kyiv and Chernihiv, a northern Ukrainian city, as a confidence-building measure, the most significant concession by Moscow since invading its neighbor more than a month ago.

In the clearest sign yet of progress in their cease-fire talks, Ukrainian negotiators said the war-torn country is prepared to give up on joining the North Atlantic Treaty Organization and adopt a neutral stance in return for security guarantees.

Turkish President Recep Tayyip Erdogan speaks ahead of the peace talks between delegations from Russia and Ukraine at Dolmabahce Presidential Office in Istanbul, Turkey on March 29, 2022. (Turkish Presidency/Murat  Cetinmuhurdar/Handout/Anadolu Agency/Getty/Kyodo)

CNN reported Russia is beginning to withdraw some forces from the area around Kyiv as part of what the United States has deemed a major strategy shift by Moscow, citing two senior U.S. officials.

But U.S. President Joe Biden remains skeptical of the Russian military moves.

Asked if the reported development is the beginning of the war coming to an end, Biden told reporters at the White House, "I don't read anything into it until I see what their actions are. We'll see if they follow through on what they're suggesting."

Following cease-fire talks between representatives of Russia and Ukraine in Istanbul, Deputy Defense Minister Alexander Fomin was quoted by Russia's Tass news agency as saying, "The Russian Defense Ministry has made a decision to cardinally, several-fold decrease the military activity."

Fomin said talks on preparing an agreement on Ukraine's neutrality and non-nuclear status, as well as providing the country with security guarantees, are moving to a practical sphere, according to the news agency.

Ukrainian negotiators named countries such as Israel, Poland, Canada, and Turkey as candidates for providing such guarantees and proposed that Crimea's status, which Russia annexed in 2014, be resolved in talks over the next 15 years.

Vladimir Medinsky, who heads the Russian delegation, said there is the possibility of a meeting between President Vladimir Putin and Ukrainian President Volodymyr Zelenskyy if a peace deal is drafted.

He added that the latest talks, the fourth held between senior officials of the two countries in person since late February, were "constructive." The talks were initially set for two days but concluded Tuesday.

The sign of progress comes as the death toll has neared 5,000 in the southeastern port city of Mariupol, and a Russian strike blasted a hole in a nine-story government building in Mykolaiv on Tuesday, according to local media.

Russia has demanded that Ukraine demilitarize, and its Foreign Minister Sergey Lavrov said Monday that the elimination of anti-Russian ideology must also be included in the envisioned agreement.

Turkish Foreign Minister Mevlut Cavusoglu was quoted by Reuters news agency as saying Tuesday's talks marked the "most significant progress" in Ukraine-Russia negotiations to date.

Ukrainian and Russian negotiators held the first in-person cease-fire meeting since March 7 as Russia's invasion of the Eastern European country enters its fifth week.