Russia's lower house of parliament has given key support to a bill banning Americans from adopting children, resulting in a huge outcry from rights groups.
The bill, which came in retaliation for a US measure that punishes Russia for its rights record under President Vladimir Putin, was approved by 400 MPs in the 450-seat chamber.
Only four deputies voted against the bill while two parliamentarians in the Kremlin-controlled legislature abstained.
The bill now needs to be passed in the largely symbolic third reading on Friday before moving on to the upper house of parliament, which often gives unanimous approval to Kremlin-sponsored legislation.
Putin will then need to sign the bill before it enters into law, possibly as early as the start of next year.
The tough measure bans adoption of Russian children by US families, ends the bilateral adoption agreement between the two countries, and forbids US adoption agencies from working in the Russia.
With several dozen people protesting outside, police officers placed the Duma building under virtual lockdown, bringing reinforcements in anticipation of large rallies.
While Putin last week welcomed the parliament's decision to retaliate against the so-called Magnitsky Act, named in honour of a whistle-blowing lawyer who died in jail before going on trial, the Kremlin was more ambiguous about supporting the measure on Wednesday.
Putin's spokesman Sergei Peskov told state television that 'the line of the executive branch of the government is more restrained' than that of the pro-Kremlin MPs in the Duma.
Speaking ahead of Putin's press conference on Thursday, which is also expected to address the bill, Peskov added however that 'such a tough emotional reaction by Russian parliament members is quite understandable.'
Unusually, several political heavyweights, including Education Minister Dmitry Livanov, opposed the bill, publicly saying that an 'eye-for-an-eye logic' would put at risk children who fail to find adoptive parents in Russia.
Of the 3400 Russian children adopted by foreign families in 2011, 956 - nearly a third - were adopted by Americans, according to official figures. Eighty nine of those adopted were disabled children.
Although Russian adoptions have declined over the past five years due to increased regulations, Russia is still the third largest source of adoptions for the United States, according to official figures.