MOSCOW -- The upper chamber of Parliament on Wednesday unanimously approved a bill to ban adoptions of Russian children by United States citizens, sending the measure to President Vladimir V. Putin, who has expressed support but not yet said if he will sign it.
Enactment of the adoption ban, which was developed in retaliation for an American 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 to 0, with 43 senators absent. By law, Mr. Putin has two weeks to act on the bill, but a decision is expected sooner. The bill calls for the ban to take effect on Jan. 1.
The American 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," Mr. McFaul wrote. "Saddened by Federal Council vote today."
Since Mr. Putin returned to the presidency in May, Russian officials have used a juggernaut of legislation and executive decisions to curtail United States influence and involvement in Russia, undoing major partnerships that began after the fall of the Soviet Union.
In September, the Kremlin ordered the United States Agency for International Development to cease operations here, shutting a wide portfolio of public health, civil society and other initiatives. And officials announced plans to terminate a joint effort to dismantle nuclear, chemical and other nonconventional weapons known as the Nunn-Lugar agreement.
Russia also passed a law requiring nonprofit groups that get financing from abroad to register as "foreign agents," sharply limiting the ability of the United States to work with good-government groups, and another law broadening the definition of treason to include "providing financial, technical, advisory or other assistance to a foreign state or international organization."
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 on 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 parents from the United States in 2011, more than any other country, and more than 45,000 such children have been adopted by American parents since 1999.
Pavel Astakhov, Russia's child rights commissioner, told news agencies on Wednesday that if enacted, the ban could prevent the departure of 46 children who were ready to be adopted by parents from the United States. Some of those adoptions have already received court approval, he said, raising the specter of wrenching emotional turmoil for the families involved.
"The children who have been chosen by foreign American parents -- we know of 46 children who were seen, whose paperwork was processed, who came in the sights of American agencies," Mr. Astakhov said in his statement. "They will not be able to go to America, to those who wanted to see them as their adopted children. There is no need to go out and make a tragedy out of it."
Mr. Astakhov, who is a longtime advocate of restricting international adoptions, said he would seek to extend the ban to all countries. "I think any foreign adoption is bad for the country," he said.
That remark prompted Sergei Parkhomenko, a well-known journalist and commenter, to reply tartly, "Adoption when needed is for the good of the child, not the good of the country." And he accused Mr. Astakhov of neglecting his duty to serve children in favor of serving Mr. Putin, who appointed him.
Some Russian lawmakers said that they believed that the bilateral agreement on adoptions with the United States would be void as of Jan. 1, even though Mr. Putin, at his annual news conference last week, said changes to the agreement 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 huge public outcry and debate, with critics of the ban saying it would most hurt Russian orphans, many of whom are already suffering in the country's deeply troubled child welfare system.
In their debate on Wednesday, lawmakers said they felt compelled to retaliate for a law signed by President Obama earlier 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.
Lawmakers also said that Russia, which has more than 650,000 children living without parental supervision, should take care of them on its own. At the same time, the lawmakers acknowledged the flaws in the system and on Wednesday adopted a resolution calling for measures to make adoption by Russian citizens easier.
"The attitude toward the protection of parenthood and childhood has to change drastically on every level," the resolution said, citing excessive bureaucracy, lack of financing for children's medical care and insufficient efforts to promote adoption.
"We need to set a plan for the future," said Valery V. Ryazanksy, a senator from the Kursk region. Then, reiterating a slogan adopted by many lawmakers in recent days, he declared, "Russia without orphans!" Gennady I. Makin, a senator from Voronezh, gave it a slight twist: "Russia without orphanages."
Child welfare advocates have mocked this sort of rhetoric, noting that more than 80,000 children were identified as in need of supervision in 2011 and that the country had been unable to find homes for the vast majority of 120,000 children eligible for adoption.
There were slightly more than 10,000 adoptions in Russia in 2011, about 3,400 of which were by foreigners.
In addition to banning adoptions by Americans, the bill approved on Wednesday would impose sanctions on American judges and others accused of violating the rights of adopted Russian children in the United States.
A number of cases involving the abuse or even deaths of adopted Russian children in recent years have generated publicity and outrage in Russia, including a case in which a 7-year-old boy was sent on a flight back to Russia alone by his adoptive mother in Tennessee.
The Russian law was named for Dmitri Yakovlev, a toddler who died of heatstroke in Virginia in 2008, after his adoptive father left him in a parked car for nine hours. The father, Miles Harrison, was acquitted of manslaughter by a judge who ruled that the death was an accident.
But the focus on adopted children also showed the Russian government as largely vexed in trying to find a reciprocal response to the new American human rights law. Russians, especially wealthy ones, travel often to the United States and own property there, but Americans travel in relatively small numbers to Russia and typically do not maintain financial assets here.
This article originally appeared in The New York Times.