The US says there has been no formal response from the Kremlin to fresh proposals aimed at easing Russiaâ€™s concerns over a proposed Europe-based missile shield.
Earlier, an unidentified Kremlin official claimed the offer contained nothing new and negotiations would have to wait until Barack Obama was sworn in.
Russia said last week it would deploy missiles in its enclave of Kaliningrad near the Polish border in retaliation for U.S. plans to install elements of its proposed missile defence shield in Poland and the Czech Republic.
Since then, Moscow has seemed to soften its stance â€“ but the position is still unclear after Washington tabled a fresh deal at the start of the week. Observers say it built on previous plans to allow Russian access to the shield sites.
The Americans say the shield is needed to protect the US against attack from what it calls â€œrogue statesâ€ â€“ taken by many to mean Iran and North Korea.
Officials say Iranâ€™s announcement that it had test-fired a new generation of surface-to-surface missiles on Wednesday was a further reminder of the shieldâ€™s importance