Two weeks ago, the Organization for Security and Cooperation in Europe accepted Moscow's invitation to allow 70 observers - a significantly smaller number from previous elections - for the Dec. 2 vote.
An initial team of 20 experts immediately applied for visas on Nov. 2 and Nov. 5, but has yet to receive them, said Urdur Gunnarsdottir, spokeswoman for the OSCE's Warsaw-based Office for Democratic Institutions and Human Rights, which organizes observer missions.
"We were hoping for as close to immediate deployment as possible," Gunnarsdottir said. "We realize it takes some time to issue visas, but we have not received anything."
The experts are normally the first observers on the ground, where they monitor the pre-election campaign, candidate registration and media coverage before the vote, Gunnarsdottir said.
The delays give experts little time to do so, she said, noting that candidate registration has already finished.
Russian consular authorities have said only that they are "awaiting instructions" from Moscow, she said.
Asked whether the OSCE may not send any observers due to the holdup, she said: "I can't exclude anything at the moment."
"We certainly hope that we will get visas and that we will be able to send people to Moscow, but we really need to be able to move quickly now on this."
The OSCE has not encountered such delays in getting visas for such missions before, Gunnarsdottir said.
"All of this is new for us, everything from the delayed invitations to the restrictions."
Igor Borisov, a member of the Russian Central Elections Commission, said in Moscow that Russia is "interested" in hosting observers, and suggested there was nothing exceptional in the visa delay.
"We all understand that the procedure for issuing of visas takes place under certain procedures ... and that requires time," Borisov was quoted as saying by the Interfax news agency.
Borisov said the Foreign Ministry is responsible for issuing visas, and said the elections commission is "trying to clarify the circumstances" of the delay described by the OSCE.
The OSCE - which includes 56 countries from Europe, central Asia and North America - sent 400 observers for Russia's last parliamentary election in 2003. The observers described that vote as a step backward for democracy.