Russian President Vladimir Putin on Friday signed into law controversial parliamentary legislation banning the adoption of Russian children by American families, the Kremlin said.
The law - retaliation for a US law punishing Russian officials implicated in the 2009 prison death of the whistle-blowing attorney Sergei Magnitsky - will come into force on 1 January, it said.
The highly contentious law is seen as the toughest piece of anti-US legislation during Putin's 13-year rule and has prompted objections not just from activists but even some cabinet ministers.
A particular subject of concern are the dozens of Russian children who are now in an agonising limbo after being prepared for US adoption but who now are effectively banned from leaving for their new lives.
The Kremlin children's rights envoy Pavel Astakhov said a total of 52 Russian children who had been prepared for US adoption should now go to Russian parents specially selected by regional governors.
"I believe they should be adopted in Russia," Astakhov, a key backer of the legislation, told Interfax.
The law had been passed in three readings by the State Duma, the lower house of parliament, and then at a session Wednesday held by the Federation Council or upper house.
Putin said on Thursday that he intended to sign it, ending days of speculation about his position.
Pro-Kremlin lawmakers put together the bill in a matter of days in response to a new US law sanctioning Russian officials implicated in Magnitsky's death.
Its passage revealed cracks in the Russian leadership between those who would prefer to get tough with the United States and ministers who back a more cautious approach.
Foreign Minister Sergei Lavrov and the cabinet's social affairs chief, Deputy Prime Minister Olga Golodets, have both spoken out against it.
By apparent coincidence, a Moscow court on Friday also acquitted the former deputy chief of a Moscow prison where Magnitsky was held over causing his death by negligence.
Dmitry Kratov was the only Russian official to still be facing charges over the Magnitsky case.
A separate measure in the law targets Russia's liberal activists by banning all domestic political organisations with funding from the United States.
Putin on Thursday had mounted a firm defence of the ban on US adoptions while accusing the United States of "acting brazenly and arrogantly" towards Russia.
He said those who believed the law limited the opportunities of orphans failed to see the threats to Russian society posed by a steady outflow of children.
"There are lots of places in the world where living standards are higher than they are here," said Putin.
"And what - are we going to send all our children there? Perhaps we should move there ourselves?"
And he raised the spectre of Russia going to "ruin" if it continued to allow foreigners to take care of its young.
"It may seem like our resources are limitless. But this is not the case," Putin told the government's most senior members in a televised meeting.
"We may reach a certain point at which - once we overstep it - we will not be able to stop our ruin," he warned.
"So we have to be extremely sensitive and attentive toward such things."
US families adopted nearly 1000 Russian children last year and are the number one foreign destination of the country's orphans.
Putin also signed a decree Friday on measures to protect orphans in Russia, part of a clear drive for all orphans in the country to be brought up in Russian families.
Astakhov has also raised the prospect of Russia banning foreign adoptions altogether once the new orphan support programme is in place.
"We will be ready to do that (eliminate foreign adoptions) after the adoption of the federal targeted programme on orphans," Interfax quoted Astakhov as saying on Thursday.