The first lady, Melania Trump, revealed on Friday that she has been having back-channel talks with President Vladimir V. Putin of Russia for three months, beseeching him to return children separated from their families because of his war on Ukraine.

“President Putin and I have had an open line of communication regarding the welfare of these children,” Mrs. Trump said in remarks from the grand foyer of the White House.

She claimed that in the past 24 hours, eight children were reunited with their families. “Plans are already underway to reunify more children in the immediate future,” she added. She spoke for six minutes.

In Russia, Mrs. Trump’s comments were carried on the news, but there was no immediate statement about the negotiations by the Kremlin.

The mass abduction of Ukrainian children has been one of the ghastlier aspects of the war, which has raged for more than three years. Ukraine has said it identified the names of thousands of children — more than 19,000 by one estimate — who were taken into Russia or Russian-controlled territory.

Mrs. Trump said the “identities and circumstances” of the eight children were verified by the U.S. government. She said three of them “were separated from their parents and displaced to the Russian Federation because of frontline fighting; the other five were separated from family members across borders because of the conflict, including one young girl who has now been reunited from Ukraine to Russia.”

Mrs. Trump said she also “raised concerns” about minors who were displaced to Russia when the war broke out but who have since reached adulthood. “Given the dangers of traversing this war-torn region, their safe return requires coordinated assistance,” she said, adding that Russia has signaled openness to working with her on that, too.

“I have learned a lot about this matter during the past three months,” she said.

The circumspect first lady, who grew up behind the Iron Curtain in Slovenia, has shown a particular interest in this war. In August, she wrote a letter to Mr. Putin expressing her concern about children affected by the war and had her husband hand-deliver it to him during his summit with the Russian autocrat in Alaska.

“Much has unfolded since President Putin received my letter last August,” Mrs. Trump explained. “He responded in writing, signaling a willingness to engage with me directly.”

But in recent months President Trump has expressed flashes of anger, frustration and even betrayal with Mr. Putin for stringing him along. “He’s really let me down,” Mr. Trump said last month.

In the past, Mr. Trump has described his wife’s interest in ending the war and her skepticism of Mr. Putin and his empty promises. “I go home,” Mr. Trump recounted in July, “I tell the first lady: ‘You know, I spoke to Vladimir today. We had a wonderful conversation.’ She said: ‘Oh, really? Another city was just hit.’”

Moments after Mrs. Trump finished speaking on Friday, Mr. Trump posted a video of Mr. Putin that had nothing to with the children reunited with their families or Mrs. Trump’s address.

The video showed Mr. Putin praising Mr. Trump’s abilities to “solve complex problems” and “crises that last for decades.”

“Thank you to President Putin!” Mr. Trump wrote.