"Russia believes that only an agreement that contains effective tools for Russian and U.S. officials to monitor the living conditions of adopted Russian children will ensure that recent tragedies in the United States will not be repeated," he said.
But the Russia Education and Science Ministry, which oversees international adoptions, said it had no knowledge of an official freeze. A spokeswoman for the Kremlin's children's rights ombudsman said that organization also knew nothing of a suspension.
And in Washington, the U.S. State Department said the administration had gotten conflicting information when it sought clarification from Russian officials about the status of adoptions. Spokesman P.J. Crowley said the U.S. was continuing to seek clarification. "Right now, to be honest, we've received conflicting information," he said.
The boy's return — with little supervision or explanation, aside from a note he carried from his adoptive mother saying he had psychological problems — outraged Russian authorities and the public.
Russia has a large population of abused and neglected children, many of them the children of alcoholics. Many of these children wind up living in large institutions, because adoption by Russian families is still relatively uncommon.
But as Russia has prospered over the past decade, the fate of these children, especially of those sent abroad, has increasingly been the focus of concern.
Russian lawmakers for years have suggested suspending foreign adoptions, citing a few high-publicized cases of abuse and killings of Russian children adopted by U.S. families.
The Tennessee woman who sent back her adopted Russian son last Thursday claimed she had been misled by his Russian orphanage about his condition.
Russians were outraged that no charges were filed against her in the United States.
"How can we prosecute a person who abused the rights of a Russian child abroad?" the children's rights ombudsman, Pavel Astakhov, said in a televised interview Wednesday. "If there was an adoption treaty in place, we would have legal means to protect Russian children abroad.
Some 3,000 U.S. applications for adopting Russian children are now pending, according to the Joint Council on International Children's Services, which represents many U.S. agencies engaged in international adoption.
But the numbers have declined sharply in recent years — with only 1,586 U.S. adoptions from Russia last year, compared with more than 5,800 in 2004.
The decline is due in part to concerns by U.S. parents about reports of fetal alcohol syndrome and other problems faced by some Russian children.
Thousands of American adoption advocates had hoped this week to petition Russian and U.S. leaders to prevent the halt in adoptions announced Thursday. Poignant pleas from would-be adoptive parents were included in an online petition, signed by more than 11,000 people and addressed to President Obama and his Russian counterpart Dmitry Medvedev, the council said.
U.S. officials appeared willing to consider Russia's demand for a formal bilateral adoption pact, after years of resisting such entreaties while arguing that an international accord called the Hague Convention would be sufficient once Russia ratified it.
"We're willing to talk about some sort of bilateral understanding where we would ensure that these kinds of things could not happen," the U.S. ambassador to Russia, John Beyrle, told CBS television this week.
Crowley said that the group of U.S. officials from the State Department and the Department of Homeland Security will be traveling to Moscow this weekend for meetings early next week with Russian officials to clarify the situation.
"We're really going to Moscow next week to address what are serious and legitimate concerns about our processes regarding adoptions between Russia and the United States," he said. "We certainly think that there are many thousands of Russian children who are not adopted by Russian families; we have the same objective as Russia has: to find loving, safe and permanent homes, some of which would be here in the United States."