Putin has strongly hinted he will sign the bill, which would also outlaw some US-funded non-governmental groups and impose visa bans and asset freezes on Americans accused of violating the rights of Russians.

The Federation Council, Russia's upper house of parliament, voted unanimously to approve the bill, which has clouded US-Russia relations and outraged Russian liberals who say lawmakers are playing a political game with the lives of children.

US-Russia ties are already strained over issues ranging from Syria to the Kremlin's treatment of opponents and restrictions imposed on civil society groups since Putin, in power since 2000, began a new six-year term in May.

The bill has also drawn unusual criticism from senior government officials including Foreign Minister Sergei Lavrov and Olga Golodets, a deputy prime minister who warned the Kremlin that it may violate an international convention on children's rights.

Lavrov said last week that the ban would be "wrong", and that Russia should stand by a long-awaited bilateral accord that improves its ability to keep tabs on children adopted by Americans, which entered into force on November 1.

But Lavrov appears to have backed down. Foreign Ministry officials said on Wednesday that the bill would not violate the 1989 Convention on the Rights of the Child, and Russia would take steps to halt the bilateral agreement.

Putin has described the bill as an emotional but appropriate response to US legislation he said was poisoning relations.

US President Barack Obama this month signed off on the Magnitsky Act, which imposes visa bans and asset freezes on Russians accused of human rights violations, including those linked to the death in custody of an anti-graft lawyer in 2009.

The ban on American adoptions takes Russia's response a step further, playing on deep sensitivity among Russians - and the government in particular - about adoptions by foreigners, which skyrocketed after the 1991 Soviet collapse.

The bill is named after Dima Yakovlev, a Russian-born toddler who died of a heat stroke when his adoptive American father forgot him in a car. He is one of 19 Russian-born children Moscow says have died "at the hands of US citizens" in a decade, in cases that have been prominently featured in Russian state media.

In a poll conducted on December 23 by the Moscow-based Public Opinion Foundation, 75 percent of respondents said Russia should ban or place additional restrictions on foreign adoptions.

"It is immoral to send our children abroad to any country," Valery Shtyrov, a Federation Council deputy, said in a one-sided debate peppered with hawkish rhetoric before the 143-0 vote.

Children's rights advocates say the law, due to take effect on January 1 if signed by Putin, will deprive children of a way out of Russia's overcrowded orphanage system.

"This is the most vile law passed since Putin came to power," opposition activist Boris Nemtsov said, saying he was certain the president would sign it. "Putin is taking children hostage, like a terrorist."

Police said they had arrested seven people protesting against the law on Wednesday outside the Federation Council.

Nevertheless, lawmaker Gennady Makin said the Magnitsky Act demanded a tough response.

"He who comes to Russia with a sword dies by that sword," he said.

The Russian bill would outlaw US-funded "non-profit organizations that engage in political activity", which Putin accuses of trying to influence Russian politics.

Russia ejected the United States Agency for International Development, which funds Russian non-governmental groups, in October, and Putin has signed a law forcing many foreign-funded organizations to register as "foreign agents" - a term that evokes the Cold War.

Americans affected by the visa ban could include those involved in the prosecution of Viktor Bout, a Russian arms dealer serving a 25-year prison term in the United States after an arrest and trial condemned as unfair by Moscow.

Reuters