MOSCOW — The upper chamber of Parliament on Wednesday unanimously approved a bill to ban adoptions of Russian children by US citizens, sending the measure to President Vladimir Putin, who has voiced support but not yet said if he will sign it.
Enactment of the adoption ban, which was developed in retaliation for a US law punishing Russians accused of violating human rights, would be the most severe blow yet to relations between Russia and the United States in a year marked by a series of setbacks.
The vote in the Federal Council was 143-0, with 43 senators absent. By law, Putin has two weeks to act on the bill, but a decision is expected sooner. The bill calls for the ban to take effect Tuesday.
The US ambassador, Michael A. McFaul, who criticized the bill after the lower house passed it last week, posted a more restrained comment on Twitter on Wednesday noting the fierce disagreement that has erupted within Russian government and society.
‘‘I agree with hundreds of thousands of Russians who want children removed from political debate,’’ McFaul wrote. ‘‘Saddened by Federal Council vote today.’’
Since Putin returned to the presidency in May, Russian officials have used a juggernaut of legislation and executive decisions to curtail US involvement in Russia, undoing major partnerships that began after the fall of the Soviet Union.
The adoption ban, however, is the first step to take direct aim at the American public and would effectively undo a bilateral agreement on international adoptions that was ratified this year and took effect Nov. 1. That agreement called for heightened oversight in response to several high-profile cases of abuse and deaths of adopted Russian children in the United States.
About 1,000 Russian children were adopted by US parents in 2011, more than any other country.
Pavel Astakhov, Russia’s child rights commissioner and a major proponent of the ban, told news agencies Wednesday that he expected it to be enacted and to immediately block the departure of 46 children ready to be adopted by parents from the United States. He said the adoptions would be blocked regardless of previous agreements with the United States and even though some of the adoptions had already received court approval. He expressed no regrets over the likely emotional turmoil for the families involved.
“There is no need to go out and make a tragedy out of it,’’ he said.
Some Russian lawmakers said they believed that the bilateral agreement on adoptions with the United States would be void as of Tuesday, even though Putin has said changes to the pact required one-year notice by either side.
The proposed ban has opened a rare split at the highest levels of the Russian government, with several senior officials speaking out against it. And it has provoked a public outcry and debate, saying it would hurt Russian orphans, many of whom are already suffering in the country’s deeply troubled child welfare system.
On Wednesday, lawmakers said they felt compelled to retaliate for a law signed by President Obama this month that will punish Russian citizens accused of violating human rights, by prohibiting them from traveling to the United States and from owning real estate or other assets there. A major proponent of the law in Congress was Representative James McGovern, Democrat of Worcester.
Child-welfare advocates have noted that more than 80,000 children were identified as in need of supervision in 2011 in Russia and that the country had been unable to find homes for the vast majority of 120,000 children eligible for adoption.
In addition to banning adoptions by Americans, the bill would impose sanctions on US judges and others accused of violating the rights of adopted Russian children in the United States.