Russia is seeking "unprecedented" curbs on monitors observing its parliamentary polls, the Organization for Security and Co-operation in Europe (OSCE) says.
Mr Putin last week said OSCE observers would be invited
Moscow wants limits on the size of the OSCE delegation at the 2 December poll, and consultation on its make-up.
"This is not business as usual," an OSCE spokeswoman said, adding that such conditions could seriously limit the chance for "meaningful observation".
Washington has criticised Russia's move to limit the OSCE watchdogs' role.
"We are concerned and disappointed by the belated timing and the conditional nature of Russia's invitation to election observers," White House spokeswoman Dana Perino said.
"Any conditions that are placed on them are a concern to us and we will certainly be bringing this up with the Russians," she said.
The OSCE international security body often sends monitors to elections. Its 56 member states come from Europe, Central Asia and the US and Canada.
The body typically sends a delegation of election observers to a country after receiving an official invitation.
The OSCE says it does not enter into discussions on the size and composition of the delegation.
'Ready for dialogue'
Urdur Gunnarsdottir, spokeswoman for the OSCE Office for Democratic Institutions and Human Rights, said the terms suggested in the Russian letter were unprecedented.
"We have to consider its implications," she told the BBC News website.
Ms Gunnarsdottir quoted the letter as saying Moscow was "ready for a dialogue on the composition of the mission".
She said the letter from the Central Election Commission in Moscow also suggested that the OSCE delegation "could comprise up to 70 persons" - far short of the 465 sent to Russia's last parliamentary elections four years ago.
December's elections are expected to deliver victory to United Russia, the largest party loyal to President Vladimir Putin.
Mr Putin, who steps down as president next year, is popular among many Russians for his economic and foreign policies.
However, opposition groups and human rights activists have accused him of resurrecting Soviet-era authoritarianism.
United Russia said on Tuesday that it will not take part in televised debates with rival parties.
"We are indeed not going to participate in the debates," party official Andrei Vorobyov said.
"We intend to use the time allotted by the law for explaining the main thing to voters - Putin's plan," Mr Vorobyov told Interfax news agency.
Russia media reports say the debates have been scheduled for off-peak viewing times such as mid-morning or late at night.
All 11 parties contesting the December election are entitled to TV airtime to put across their views.
Lyudmila Alexeyeva, the head of the Moscow Helsinki Group, a human rights body, told Ekho Moskvy radio the leaders of United Russia "don't have political convictions" and therefore "cannot engage in a political debate".