The bill is part of the country's increasingly confrontational stance with the West and has angered some Russians who argue it victimizes children to make a political point.
The law would block dozens of Russian children now in the process of being adopted by American families from leaving the country and cut off a major route out of often-dismal orphanages. The U.S. is the biggest destination for adopted Russian children – more than 60,000 of them have been taken in by Americans over the past two decades.
"I still don't see any reasons why I should not sign it," Putin said at a televised meeting. He went on to say that he "intends" to do so.
UNICEF estimates that there are about 740,000 children not in parental custody in Russia, while only 18,000 Russians are now waiting to adopt a child. Russian officials say they want to encourage more Russians to adopt Russian orphans.
Children's rights ombudsman Pavel Astakhov on Thursday petitioned the president to extend the ban to other countries.
"There is huge money and questionable people involved in the semi-legal schemes of exporting children," he tweeted.
Kremlin critics say Astakhov is trying to extend the ban only to get more publicity and win more favors with Putin. A graduate of the KGB law school and a celebrity lawyer, Astakhov was a pro-Putin activist before becoming children's rights ombudsman and is now seen as the Kremlin's voice on adoption issues.
"This is cynicism beyond limits," opposition leader Ilya Yashin tweeted. "The children rights ombudsman is depriving children of a future."
The bill is retaliation for an American law that calls for sanctions against Russian officials deemed to be human rights violators.
The U.S. law, called the Magnitsky Act, stems from the case of Sergei Magnitsky, a Russian lawyer who died in jail after being arrested by police officers whom he accused of a $230 million tax fraud. The law prohibits officials allegedly involved in his death from entering the U.S.
Kremlin critics say that means Russian officials who own property in the West and send their children to Western schools would lose access to their assets and families.
Putin said U.S. authorities routinely let Americans suspected of violence toward Russian adoptees go unpunished – a clear reference to Dima Yakovlev, a Russian toddler for whom the adoption bill is named. The child was adopted by Americans and then died in 2008 after his father left him in a car in broiling heat for hours. The father was found not guilty of involuntary manslaughter.
The U.S. State Department says it regrets the Russian Parliament's decision to pass the bill, saying it would prevent many children from growing up in families.
Astakhov said Wednesday that 46 children who were about to be adopted in the U.S. would remain in Russia if the bill comes into effect.
The passage of the bill follows weeks of a hysterical media campaign on Kremlin-controlled television that lambasts American adoptive parents and adoption agencies that allegedly bribe their way into getting Russian children.
A few lawmakers claimed that some Russian children were adopted by Americans only to be used for organ transplants and become sex toys or cannon fodder for the U.S. Army. A spokesman with Russia's dominant Orthodox Church said that the children adopted by foreigners and raised outside the church will not "enter God's kingdom."
Critics of the bill have left dozens of stuffed toys and candles outside the parliament's lower and upper houses to express solidarity with Russian orphans.