Medvedev's spokeswoman Natalya Timakova said on Thursday that when he signed the New START treaty with President Barack Obama, they agreed that the ratification process should be conducted simultaneously.
She said that Medvedev voiced hope that both houses of Russian parliament would ratify the pact, but added that they would need some time to analyse the Senate's conditions for its ratification before making their decision.
Legislators in the Kremlin-controlled parliament had said before the Senate landmark ruling on Wednesday that they would approve the treaty quickly after it was ratified in the US
Lower house speaker Boris Gryzlov, however, told reporters on Thursday that the Senate's ratification resolution contained some conditions and the legislators need to study the text carefully before making their decision.
He added that the State Duma may ratify the pact on Friday if the text of the treaty itself remained unchanged.
"If these conditions don't change the text of the treaty, we may pass a ratification bill even tomorrow," Gryzlov said.
He said that the house would need more time if it finds any changes in the body of the treaty.
Conservative Republicans said the pact would limit US options on missile defence, lacked sufficient procedures to verify Russia's adherence and deserved more time for consideration.
Obama called the treaty a national security imperative and pressed strongly for its approval before Congress, with a Republican majority, assumes power in January. In recent days, he had telephoned a handful of wavering Republicans, eventually locking in their votes.
The Obama administration has argued that the United States must show credibility in its improved relations with its former Cold War foe, and the treaty was critical to any rapprochement. The White House is also counting on Russia to help pressure Iran over its nuclear ambitions.
Republicans had tried to kill the treaty by forcing changes in its language that would have sent it back for negotiations with Moscow. Democrats sought to appease some Republican senators by letting them raise these issues in legislation accompanying the treaty that would not directly affect the pact.
On Wednesday, two such amendments, one on missile defence and one on funding for the US nuclear arsenal, passed with support from both parties.
Konstantin Kosachev, the head of the Duma's foreign affairs committee, said that decision was conditioned on the analysis of the amendments.
"We realise that the process shouldn't be delayed, but we intend to work in such a way that it doesn't affect the quality," he said.
Kosachev said that the Duma may quickly approve the pact on Friday without any conditions, or could decide to include some conditions of its own, which could delay the vote.
Retired General Vladimir Dvorkin, who helped negotiate previous arms deals with the United States, predicted that the Kremlin-controlled parliament would quickly ratify the New START.
"This treaty is important for the Russian leadership because it formally preserves the nuclear balance with the United States, the last attribute of a superpower," Dvorkin said, according to the Interfax news agency.