Russian President Vladimir Putin told his Finnish counterpart that it would be a “mistake” for Finland to join NATO, according to statement from the Kremlin.

The two leaders spoke by phone on Saturday as U.S. Senate minority leader Mitch McConnell led a delegation of Republican senators on a visit to Ukraine. Ukrainian President Volodymyr Zelenskyy said the visit was a powerful signal of bipartisan American support for Ukraine, according to the Ukrainian presidential administration.

Putin Warns Finland Joining NATO Would Be ‘Mistake’

Meanwhile, Russian troops began withdrawing from the heavily contested northeastern city of Kharkiv after weeks of shelling. The Ukrainian military said Russian troops are pulling back from Ukraine’s second-largest city and are focusing on protecting supply routes, while launching attacks in the eastern Donetsk region to “deplete Ukrainian forces and destroy fortifications.”

Putin Warns Finland Joining NATO Would Be ‘Mistake’

Ukraine “appears to have won the Battle of Kharkiv,” the Institute for the Study of War, a Washington-based think tank, said.

Putin Warns Finland Joining NATO Would Be ‘Mistake’

The call between Finland President Sauli Niinisto and Putin about the Scandanavian country’s desire to join NATO was initiated by Finland, according to a statement released by Niinisto’s office.

"The conversation was direct and straightforward and it was conducted without aggravations. Avoiding tensions was considered important," Niinisto was quoted as saying in a statement by his office.

A Kremlin statement released after the call said Putin told Niinisto that abandoning Finland’s policy of neutrality would have a negative impact on Russian-Finnish relations.

Niinisto and Finnish Prime Minister Sanna Marin said Thursday that they want the country to join NATO "without delay," a move that would be a major policy shift for the traditionally neutral country in response to Russia's invasion of Ukraine.

"Putin stressed that the end of the traditional policy of military neutrality would be a mistake since there is no threat to Finland's security," the Kremlin statement said.

Sweden, another traditionally neutral Scandinavian country, is also expected to ask to join NATO in the coming days.

The possible expansion of NATO will be a focus of talks Saturday, as U.S. Secretary of State Antony Blinken heads to Berlin for an informal NATO foreign ministerial meeting.

Turkish President Recep Tayyip Erdogan said Friday his country does not support Finland and Sweden joining NATO, citing their support of what Turkey considers terrorist organizations, such as Kurdish militant groups.

"We are following developments concerning Sweden and Finland, but we are not of a favorable opinion," Erdogan told reporters in Istanbul. Any NATO enlargement requires the unanimous consent of the existing members.

U.S. officials said they were working to "clarify Turkey's position," while reiterating that the "United States would support a NATO application by Finland and/or Sweden should they choose to apply."

"We strongly support NATO's Open Door policy," U.S. Assistant Secretary of State for European and Eurasian Affairs Karen Donfried told reporters Friday. "I think that it's important to remember that a fundamental principle the U.S. is defending in terms of its support for Ukraine is the right of every sovereign country to decide its own future foreign and security policy arrangement."

Both Sweden’s and Finland's foreign ministers will be participating in the North Atlantic Council informal dinner Saturday in Berlin. From Germany, Blinken heads to France on Sunday, where he will attend the second ministerial meeting of the U.S.-EU Trade and Technology Council, known as the TTC.

U.S. President Joe Biden talked with Swedish Prime Minister Magdalena Andersson and Finland's Niinistö on Friday.

"President Biden underscored his support for NATO's Open Door policy and for the right of Finland and Sweden to decide their own future, foreign policy, and security arrangement," the White House said in a readout of the call, adding the leaders "reiterated their shared commitment to continued coordination in support of Ukraine and the Ukrainian people affected by the war."

The German Marshall Fund's Michael Kimmage told VOA that Finland’s joining NATO would shake up the security order in Europe, both for NATO and for Russia.

"It's a very, very long border, and of course it brings NATO very close to — or will bring NATO if it all goes through — very close to St. Petersburg. And at the same time, it will give NATO a lot more territory right on the Russian border to defend. So those are big steps. Those are big changes," Kimmage said.