Russia’s upper house of parliament was due Wednesday to vote for a bill barring Americans from adopting the country’s children, in retaliation for a new piece of human rights legislation in the US.

The highly contentious bill has inflamed tensions between the two former Cold War rivals at a time when Washington needs Moscow’s help to convince President Bashar al-Assad to quit power in Syria.

The draft legislation has already passed the three required readings in the State Duma lower house and is due to reach President Vladimir Putin’s desk before the end of the year.

The Federation Council upper chamber — comprised exclusively of Putin allies and ruling party members — is expected to overwhelmingly approve the measure after it was backed in a committee meeting on Tuesday.

The bill also includes a provision banning Russian political organisations that receive US funding.

The legislation came after US President Barack Obama this month signed into law the Magnitsky Act — a measure paying tribute to a Russian lawyer who died in police custody in 2009 after exposing a $235 million police embezzlement scheme.

The US law blacklists Russian officials allegedly involved in his death.

Sergei Magnitsky’s employer Hermitage Capital — once Russia’s largest Western investment fund — and family both believe that he was tortured in prison and eventually died of his beatings.

But Russian prosecutors this week moved to drop charges against the only person on trial in the case of Magnitsky’s death.

They are also due to hold hearings Thursday into a separate set of fraud charges that originally put Magnitsky under arrest.

The Russian lawmakers’ response has agitated some cabinet members and resulted in a rare rebuke of the official position by Foreign Minister Sergei Lavrov.

The head of Putin’s advisory human rights council also condemned the pending legislation as potentially unconstitutional.

The United States remains the number one foreign destination for orphans in Russia — a country that since Soviet times has relied on state-run homes for children and has a weak tradition of adoptions.

About 1,000 Russian children travelled to the United States last year.

The pending measure is due to enter into on January 1.

Russia’s commissioner of children?s rights said Wednesday that 46 children whose adoption by US families is pending would not be able to travel to their new homes if the measure becomes law.