Russia on Friday unveiled proposals to contain the United States and NATO in the former Soviet Union and Eastern Europe, calling for urgent negotiations with Washington as it amasses forces near Ukraine.

The United States said it was ready to talk but stated upfront that it disagreed with much in the far-reaching proposals, as it renewed warnings of painful reprisals if Russia invades Ukraine.

Russia released unfinished security documents -- an unusual move in diplomacy -- that call for US-led NATO alliance not to bring in new members or establish bases in ex-Soviet countries.

Deputy Foreign Minister Sergei Ryabkov said Russia was ready to hold security talks with the United States as early as Saturday.

"We are ready to immediately, even tomorrow -- literally tomorrow, on Saturday -- go for talks with the US in a third country," he told reporters, suggesting Geneva as a venue.

President Joe Biden's national security advisor, Jake Sullivan, said the United States was "fundamentally prepared for dialogue" and would coordinate closely with European allies.

"Russia has now put on the table its concerns with American and NATO activities; we're going to put on the table our concern with Russian activities that we think harm our interests and values," Sullivan said at the Council on Foreign Relations.

"That's the basis of reciprocity upon which you would pursue any kind of dialogue."

Another US official told reporters that the United States would respond "sometime next week" on a format for talks and said that Russia should already know that parts of the proposal will be "unacceptable" to Washington.

"If there is any further aggression against Ukraine, that will have massive, massive consequences and will carry a high price," the official said.

- 'Prevent incidents' -

The West says Moscow has readied some 100,000 troops near Ukraine, which has been battling a pro-Moscow insurgency in its east since 2014.

Sullivan said the United States does not assess that President Vladimir Putin, who blames NATO for the rise in tensions, has made a decision on whether to invade.

The Russian draft document addressed to NATO says its members should "commit themselves to refrain from further enlargement, including the accession of Ukraine as well as other states". 

It also insists that alliance members not conduct military activity in Ukraine or other countries in Eastern Europe, the South Caucasus and Central Asia.

Moscow and NATO, the document said, should limit the deployment of missiles, set up an emergency telephone hotline and also work to "prevent incidents" in the Baltics and the Black Sea. 

The draft said Washington should block NATO membership of any former Soviet country -- a reference to Ukraine as well as Georgia, which have both infuriated Moscow after Western tilts.

The United States and European countries have kept the door open but also made clear that Ukraine's membership in NATO is not on the cards, much to Kiev's annoyance.

- 'Impossible' demands -

In the draft, Russia said the United States should agree not to establish military bases in ex-Soviet states, including in Central Asia, which Moscow sees as its backyard and sphere of influence.

The United States leaned heavily on military facilities in ex-Soviet Uzbekistan and Kyrgyzstan to coordinate operations in Afghanistan, where it recently withdrew troops after two decades.

Political analyst Konstantin Kalachev described Russia's list of demands as "unrealistic and impossible" for the United States and NATO to meet.

These "spheres of influence are a thing of the past".

US President Joe Biden met Putin in Geneva in June, with the two leaders agreeing to seek more stable relations, but Western powers have also stood firm on backing Ukraine amid the war that has claimed 13,000 lives since 2014.

Biden has warned Putin of "sanctions like he's never seen" if an offensive is launched. 

British Prime Minister Boris Johnson, in a call Friday with Ukrainian President Volodymyr Zelensky, vowed to use all "diplomatic and economic powers" to prevent any aggression by Moscow.

Washington helps train Ukrainian forces and has committed more than $2.5 billion to bolster a military that crumbled in the face of Russia's annexation of the Ukrainian peninsula of Crimea in 2014.

A former KGB agent and loyal servant of the Soviet Union, Putin was dismayed when it fell apart, once calling the collapse "the greatest geopolitical disaster of the 20th century".