MOSCOW (Reuters) - Russia said on Thursday it was ready to send a government negotiator "at any moment" to start talks with the United States on the security guarantees it is seeking in order to defuse the crisis over Ukraine.

       Kremlin spokesperson Dmitry Peskov also said presidents Vladimir Putin and Joe Biden, who held a two-hour video call on Dec. 7, could speak again before New Year, though nothing firm had been agreed.

       Peskov said deputy foreign minister Sergei Ryabkov would "be ready to fly at any moment to any neutral country" to start talks.

       Ukraine and the United States say Russia has moved more than 90,000 troops within reach of the Ukrainian border and may be poised to invade, which Moscow denies.

       Russia says it feels threatened by growing ties between NATO and Ukraine, which wants to join the alliance, and the possibility of NATO missiles being deployed against it on Ukrainian soil.

       Asked about the possibility of talks between Putin and Ukrainian President Volodymyr Zelenskiy, Peskov repeated Moscow's position that it was unclear what the agenda for any such discussion would be.

       He said Russia's security proposals, which were handed to U.S. Assistant Secretary of State Karen Donfried in Moscow on Wednesday, consisted of two draft documents, which he described as a treaty and an agreement.

       He declined to discuss the content, telling reporters they would find out "in time".

       Russia's foreign ministry last week pointed to the likely thrust of the proposals when it said NATO should rescind a 2008 commitment to Ukraine and Georgia that they would one day become members, and promise not to deploy weapons in countries bordering Russia that could threaten its security.

       Moscow also called for the renewing of a regular defence dialogue with the United States and NATO and urged Washington to join a moratorium on deploying intermediate-range nuclear weapons in Europe.

       Ryabkov said this week that Russia would be otherwise be forced into a "confrontation" where it would have to deploy such missiles itself.

       (Additional reporting by Alexander Marrow; Writing by Mark Trevelyan and Angus MacSwan)