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Secretary of State Antony Blinken announced Wednesday that the United States has delivered written responses to demands made by Russia, saying it will be up to the Kremlin on how they want to proceed amid heightening tensions between Moscow and Ukraine.

Russia had issued a list of demands in December, including a promise to not admit Ukraine as a member of NATO and to withdraw troops from the region even as Russia continued to amass troops near the Ukraine border, increasing fears that Moscow will order an invasion of its neighbor.

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Blinken, on Wednesday, said that U.S. Ambassador to the Russian Federation John Sullivan hand-delivered the Biden administration's written responses to the Russian Ministry of Foreign Affairs in Moscow. 

Blinken said the administration is not releasing the document publicly because "we think that diplomacy has the best chance to succeed if we provide space for confidential talks." 

Secretary of State Antony Blinken greets Russian Foreign Minister Sergey Lavrov before their meeting, Friday, Jan. 21, 2022, in Geneva, Switzerland. (AP Photo/Alex Brandon, Pool)

"All told, it sets out a serious diplomatic path forward should Russia choose it," Blinken said Wednesday, including a "principled, pragmatic evaluation" of the concerns that Russia has raised.

Blinken said the document makes "clear" that there are "core principles" the United States is committed to defending, "including Ukraine's sovereignty and territorial integrity and the right of states to choose their own security arrangements and alliances." 

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"We've addressed the possibility of reciprocal transparency measures regarding force posture in Ukraine, as well as measures to increase confidence regarding military exercises and maneuvers in Europe," he said, adding that the document also address "areas where we see potential for progress, including arms control related to missiles in Europe, our interest to follow on an agreement ot the new START treaty that covers all nuclear weapons, and ways to increase transparency and stability." 

"We put these ideas forward because they have the potential, if negotiated in good faith, to enhance our security and that of our allies and partners while also addressing Russia's stated concerns through reciprocal commitments," Blinken said. "We're open to dialogue. We prefer diplomacy, and we're prepared to move forward where there is the possibility of communication, cooperation, if Russia de-escalates its aggression toward Ukraine, stops the inflammatory rhetoric, and approaches discussions about the future of security in Europe in a spirit of reciprocity." 

Members of Ukraine's Territorial Defense Forces, volunteer military units of the Armed Forces, train in a city park in Kyiv, Ukraine, on Saturday. (AP/Efrem Lukatsky)

Blinken said U.S. responses were "fully coordinated with Ukraine and our European allies and partners with whom we've been consulting continuously for weeks." 

"We sought their input and incorporated into the final version delivered to Moscow," he said, adding that NATO developed and will deliver to Moscow its own paper with "ideas and concerns about collective security in Europe." 

"That paper fully reinforces ours and vice versa," he said. "There's no daylight among the United States and our allies and partners on these matters." 

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Blinken said the State Department shared responses with Congress, and said he will be briefing congressional leaders on the responses Wednesday afternoon to consult with them on the administration's "approach."  

"As you know, there's strong bipartisan interest and deep expertise on the Hill when it comes to Ukraine and Russia, and we very much appreciate having Congress as a partner as we move forward," Blinken said. 

Blinken said he expects to speak with Russian Foreign Minister Sergei Lavrov in the coming days after Moscow has "had a chance to read the paper and is ready to discuss next steps." 

Airmen from the 4th Fighter Wing at Seymour Johnson Air Force Base, N.C. and the 48th Fighter Wing, Royal Air Force Lakenheath, England, arrive at Ämari Air Base, Estonia, Jan. 24, 2022.  (U.S. Air Force Photo by Staff Sgt. Megan Beatty)

"There should be no doubt about our seriousness of purpose when it comes to diplomacy and we're acting with equal focus and force to bolster Ukraine's defenses and prepare a swift, united response to further Russian aggression," Blinken said.

Blinken said that the actions from the Biden administration over the past week "have sharpened the choice facing Russia." 

"Should Russia choose further aggression, we step forward with more support for Ukraine's security and economy," Blinken said. "And we and our allies and partners are united across the board." 

He added: "It remains up to Russia to decide how to respond. We are ready either way." 

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As for Americans in Ukraine, an official said that they should "strongly consider leaving the country using commercial or privately available transportation options," noting that the U.S. Embassy in Kyiv is there to help "if they need it."

The State Department on Sunday ordered the evacuation of American citizens in Ukraine. Officials also ordered family members of employees at the United States Embassy in Kyiv to leave the country. The decision came after the U.K.'s Foreign, Commonwealth & Development Office announced on Saturday that it had information suggesting that the Russian government is plotting to install a pro-Kremlin leader in Kyiv.

The delivery of the United States' responses to Russian demands comes just hours after six U.S. fighter jets arrived in Estonia as part of the U.S. broader effort with NATO allies to support the Baltic Air Policing Mission as Russia continues to threaten invasion in Ukraine, United States European Command said Wednesday. 

The arrival of those jets also come as President Biden is weighing whether to deploy thousands of U.S. troops to Eastern Europe to bolster a broader NATO effort to protect allied countries bordering Russia and Ukraine. 

Defense Secretary Lloyd Austin on Monday put 8,500 U.S. troops on heightened preparedness in case of a decision to deploy. 

The troop deployment would be part of a broader NATO effort. Other NATO countries may also contribute troops to warn Russian President Vladimir Putin not to try to move into neighboring countries.

As part of the effort, Biden is also considering deploying naval vessels for NATO allies who may feel threatened. Some equipment and troops in these proposed actions would come from Europe, and some would come from the U.S.

NATO said that it is "sending additional ships and fighter jets" to Eastern Europe. This includes F-16s from Denmark, naval forces from Spain, and F-35s from The Netherlands. France is ready to send troops to Romania, which borders Ukraine to the south. 

Ukraine's territory has long been in Putin's crosshairs, especially amid recent NATO considerations of potentially allowing Ukraine to join the alliance. It is one of several post-Soviet republics in the region that shifted toward an alliance with the West after the collapse of the Soviet Union. 

Putin was in the Soviet KGB for many years before beginning his political career and has said the collapse of the Soviet Union was the "greatest geopolitical catastrophe" of the 20th century. 

Putin also stresses Russian ethnic and cultural influences in Ukraine as reasons why it should be part of Russia. That was a significant part of the justification Russia used when it illegally annexed the Crimea region of Ukraine in 2014. 

While NATO and the United States are fortifying allies, including the Baltics, it is not likely the Western alliance will send troops into Ukraine itself, where it would be at risk of a potentially major military engagement with Russia. 

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Biden administration officials told Fox News on Tuesday that they are also preparing "severe" sanctions against Russia should it invade Ukraine, which would have an "immediate and visible effect on the day they are implemented." 

"That means the gradualism of the past is out, and this time, we will start at the top of the escalation ladder and stay there," a senior administration official said. "We've made efforts to signal this intention very clearly, and I would say, a deepening selloff in Russian markets, its borrowing costs, the value of its currency market, imply default risk, reflect the severity of the economy consequences we can and will impose on the Russian economy in the event of a further invasion."